Solve 2x+3y=12 and x-b-1=17 simultaneously

The two equations are

2x+3y=12 ... (1)

x-y-1=17 ... (2)

x=17+y+1=18+y

x=18+y ... (3)

plugging value of x from (3) in (1)

2 (18+y) + 3y=12

36+2y+3y=12

36+5y=12

5y=-24

y=-24/5=-4.8

plugging this y in equation (3)

x=18+y = 18-4.8 = 13.2

Answer : x=13.2 and y=-4.8