y = 3x + 5 ....................................... 1
y = -2x - 15 ....................................... 2
Step 1
Equate equation 1 and 2 since both coefficients of y are equal
Therefore
3x + 5 = -2x - 15
Step 2
Collect like terms
3x + 2x = -15 - 5
5x = -20
x = -20/5
x = -4
Step 3
Substitute x in equation 1 to find y
y = 3x + 5
y = 3(-4) + 5
y = -12 + 5
y = -7
x = -4 and y = -7