7 help with please

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=-0.949 b=30.287 r2=0. 868624 r=-0.932 Use this to predict the number of situps a person who watches 3.5 hours of TV can do (to one decimal place)