M is a known number, solve the binary linear equations composed of 7x + 3Y = 4 and 5x-y = M-1!

M is a known number, solve the binary linear equations composed of 7x + 3Y = 4 and 5x-y = M-1!

7x+3y=4 (1)
5x-y=m-1 (2)
(1)+(2)×3
7x+15x=4+3m-3
22x=3m+1
x=(3m+1)/22
y=5x-m-1=(-7m-17)/22