4x-5y=25 -7x+3y=8

Answer 1

Multiply the first equation by 3 and the 2nd equation by 5

12x - 15y = 75

-35x + 15y = 40

Add

-23x = 115

x=-5

You can now go back to one of the original equations and get y.

P.S.

The reason for the multiplications is that 15 is the least common multiple of 3 and 5.