To find this answer, it says that Max goes to the gym 3x longer than Ann. Ann only goes to the gym for 30 minutes.
Multiply the time that Ann goes by 3 to find the time that Max goes.
30 x 3 = 90
Which means, that Max spends 90 minutes at the gym. /
(To simplify, he goes to the gym for 1 hour and 30 minutes)