10+2x=1000+1.01x     Subtract 10 from both sides

10-10+2x=1000-10+1.01x    Combine like terms

2x=990+1.01x     Subtract 1.01x from both sides

2x-1.01x=990+1.01x-1.01x     Combine like terms

0.99x=990        Divide both sides by 0.99

$${\frac{{\mathtt{0.99}}{\mathtt{\,\times\,}}{\mathtt{x}}}{{\mathtt{0.99}}}}$$ = $${\frac{{\mathtt{990}}}{{\mathtt{0.99}}}}$$

x=1000

9+10=19

It still can't equal 21

9+10=19

It can't equal 21 without a different calculation.

6xyz + 22xyz - 28xyz

Combine like terms

= 28xyz-28xyz

= 0

$${\mathtt{320}}{\mathtt{\,-\,}}{\mathtt{20}}\%{\mathtt{\,-\,}}{\mathtt{50}}\% = {\mathtt{128}}$$

320-20%=256

256-50%=128

$${\mathtt{360}}{\mathtt{\,\small\textbf+\,}}{\mathtt{3\,000}}{\mathtt{\,\times\,}}{\mathtt{0.12}} = {\mathtt{720}}$$

$${\mathtt{360}}{\mathtt{\,\times\,}}{\mathtt{0.12}}{\mathtt{\,\small\textbf+\,}}{\mathtt{3\,000}} = {\mathtt{3\,043.2}}$$

3x-4y=7, for x

3x-4y=7      Add plus 4y to both sides

3x-4y+4y=4y+7        So +4y-4y=0

3x=4y+7      Divide both side by 3

$${\frac{{\mathtt{3}}{\mathtt{\,\times\,}}{\mathtt{x}}}{{\mathtt{3}}}}$$ = $${\frac{\left({\mathtt{4}}{\mathtt{\,\times\,}}{\mathtt{y}}{\mathtt{\,\small\textbf+\,}}{\mathtt{7}}\right)}{{\mathtt{3}}}}$$    So $${\frac{{\mathtt{3}}}{{\mathtt{3}}}}$$ cancel each other

$${\mathtt{x}} = {\frac{\left({\mathtt{4}}{\mathtt{\,\times\,}}{\mathtt{y}}{\mathtt{\,\small\textbf+\,}}{\mathtt{7}}\right)}{{\mathtt{3}}}}$$     This is your answer, though you don't need the brackets and the multiplication sign between the 4 and the y, this is just the way the built in calculator formats it.

Some calculators do have a negative number input, it could have this symbol on it +/-. Each time it was pressed it would cycle through + or -.

If yours doesn't have this you can make a number a negative number by typing it within brackets and preceeded by the negative button. e.g. if i wanted to type negative 15 I would type (-15).

On its own there wouldn't be much point doing this so you could have something like this 22(-15)=-330   This would be the same as writting 22*-15=-330.

(10t⁴+14t³)+(3t³-22t⁴)

We don't really need brackets here as addition and subtraction are done at the same time in the order of operations. However, if we follow the order of operations we find that we can't do anything within the brackets as the brackets don't contain like terms that can be combined. We also find that we can't apply any of the exponents as they all apply to mixed terms of numbers and algebraic characters. All we can really do is combine like terms outside of the brackets.

We can combine 10t⁴ and -22t⁴ as they share t⁴.

We can then combine 14t³ and 3t³ as they share t³.

(10t⁴-22t⁴)+(14t³+3t³)

= -12t⁴+17t³