A spring stretches to 22 cm with a 70 g weight attached to the end. With a 105 g weight attached, it stretches to 27 cm. Which equation models the distance y the spring stretches with weight x attached to it?

simple form of the equation y= ax+b
y= (1/7)x + 12
come from 2 equation :
22= 70 a + b
27= 105 a + b