tertre

Wow, 1997-1998 and 1998-1999 are very close: 1997-1998: x+some amount, might be larger than the median income in 1998-1999.

Welcome, CPhill!

(4) Hint: Try to rearrange the equation, the first and second: Take -10y to the other side, and see what you can do.

@CPhill, 29 or -29? This was in step 2.

(2) Multiply the second equation by 2, so: -9x-14y=-29, 10x+7y=-2, -9x-14y=-29, 20x+14y=-4..

So, adding: y gets canceled, and 11x=-33, $x=-3$, so y= -9(-3)-14y=-29, 27-14y=-29, 14y=27+29, 14y=56, $y=4.$

Isn't the gap between two consecutive numbers, the same? So, $3x-x-1=\frac{1}{2}, 2x-1=\frac{1}{2}, 2x=\frac{3}{2}, x=\frac{3}{4}$ . 

We know that: $\frac{1}{a}+\frac{1}{b}=a*b$ . If we multiply the denominator by b and a, respectively, we get: $\frac{1b}{ab}+\frac{1a}{ba}=a*b$ . Suddenly, we go back to the problem, and it says: $ab=25.$ So, we have:$\frac{1a}{25}+\frac{1b}{25}=\frac{1a+1b}{25}.$ We also know that $a+b=13$ , so  $\frac{1a+1b}{25}=\frac{a+b}{25}=\boxed{\frac{13}{25}}.$

(a): 273+-22=273-22=251 Kelvin

(b): 273+0=273 Kelvin

(c): 273+-32=241 Kelvin

Plugging in the values, we get: $-2--4.1+5=-2+4.1+5=2.1+5=7.1.$

Both negatives will make positive, so: $-29+11=-18.$

This is just: $-14-10=-24.$