how to find the percentage of how much taller the giant bison is?

the equation y = 2.4x - 7.9 approximates the relationship between an adult male bison's front limb length, y, in centimetres, and the length of its humerus bone, x, in centimetres.

 

a) estimate, to the nearest centimetre, the front limb length of each bison:

• an extinct giant bison with a fossil humerus bone length of 40.2 cm

i got 89 cm

• a modern north american bison with a humerus bone lengh of 32.6 cm

70 cm

 

b) by what percent was the giant bison taller than the modern bison?