What is the gcf of 20 55 and 85

If a and b are the measures of two first quadrant angles and sin a = 4/9 and sin b = 2/5 find sin(a+b).

Tyler enjoys the fish so much that after his birthday his family decides to take him to a famous aquarium a tank at the aquarium is similar to his tank with the scale factor of 8 how many times greater is the volume of the tank at the aquarium than the volume of tyler tank

What is the answer to this question? i'm a bit stumped. also how do i do it? 5(x - 4) = 2(x + 5)