4x - y = 6
4x - 6 = y
2x - 5y = 12
2x - 5(4x - 6) = 12
2x - 20x + 30 = 12
2x - 20x = 12 - 30
-18x = -18
x = -18/-18
x = 1
4x - 6 = y
4(1) - 6 = y
4 - 6 = y
-2 = y
so the 2 lines given intersect at (1,-2)
y = p - 3x......(1,-2)...x = 1 and y = -2
-2 = p - 3(1)
-2 = p - 3
-2 + 3 = p
1 = p <===