Set up a system of equations to model this problem:
2x+y=25 (two times a number added to another number is 25)
3x-y=20 (three times the first number minus the other number is 20)
The easiest way to solve this system of equations would be to solve for y in the second equation, and substitute that value in for the first.
3x-y=20
*Subtract 3x from both sides*
-y=20-3x
*Divide both sides by -1*
y=3x-20
2x+y=25
2x+3x-20=25
*Combine likes terms*
5x-20=25
*Add 20 to both sides*
5x=45
*Divide both sides by 5*
x=45
Now, plug x into the first equation, and solve for y.
2x+y=25
2(45)+y=25
y=-65
Hope this helps!!
