Just need some help or pointers to solve these equations

Solve for 0 ≥ b ≥ 180

a) 3tanb - 5secb = 4

b) 2sinb - cosb = 2

i used auxillary angles for this question but i didnt get the right answer which was 90 and 143 degrees 8 minutes

Thankyou for any help =D