The lines x=4y−a and y=4x−b intersect at the point (1,2). What is a+b?

Answer 1

X = 4y-a = 1
4*2 - a = 1
a = 7.

Y = 4x - b = 2
4*1 - b = 2
b = 2.

a + b = 7 + 2 = 9.