y = 6.3x + 67.4
x is the ages of the boys between 2-10 years old
y is the average height
The boy is 5 years old, so you can plug in 5 into "x"
y = 6.3(5) + 67.4
y = 31.5 + 67.4
y = 98.9 The average height is 98.9 cm
