Not getting the correct answer need help

Question

A regression was run to determine if there is a relationship between hours of TV watched per day (x) and number of situps a person can do (y).

The results of the regression were:

y=ax+b

a=-1.067

b=32.771

r2=0.815409

r=-0.903

Use this to predict the number of situps a person who watches 13 hours of TV can do (to one decimal place)

Answer 1

y = ax + b

# of sit-ups = a•(# hrs TV) + b

# of sit-ups = (-1.067)(13) + 32.771 = 18.9