Let's solve for x first,
3x + 5y - 5y = 1 - 5y
3x/3 = 1/3 - 5y/3
x = 1/3 - 5/3y
Let's now plug that into the other equation,
7(1/3 - 5/3y) + 4y = -13
7/3 - 35/3y + 4y = -13
7/3 - 7 2/3y - 7/3 = -13 - 7/3
- 7 2/3y (-3/23) = -15 1/3 (-3/23)
y = 2
The answer is 2
