If I give my brother 5 dollars, then we will have the same amount of money. If instead he gives me 25 dollars, then I'll have twice as much money as he will have. How much money does my brother currently have (in dollars)?
+63 Let's make two variables, y(your money) and b(brother's money).
The first sentence creates the equation y-5 = b+5
Rearranging this equation gives me y=b+10.
The second sentence creates the equation y+25 = 2(b-25).
I can plug in y from the first equation, giving me (b+10)+25=2(b-25), which simplifying gives b+35=2b-50, which b=85, so your brother has 85 dollars.
We can check by plugging b in, getting the y value, then plugging it into the other equation.
y-5=85+5 so y=95
Plugging y=95 and b=85 into the second equation, I get 95+25=2(85-25) which is 120=120, which is true, meaning that I solved everything correct.
So your brother currently has 85.
