Question

Can anyone help me with this?

Answer 1

15)
20/8 = x / 6
x = 20 * 6 / 8 
x = 15

16)
18/54 = (x+4)/75
1/3 = (x+4) / 75
3(x+4) = 75
3x + 12 = 75
3x = 63
x = 21

SF = 54/18
SF = 3

17)
complement angles sum = 90
90 /18 = 5
so
5 x 11 = 55
5 x 7 = 35

smaller angle = 35 degrees

18)
ratio 4:5:9
4+5+9 = 18
sum of interior angles of a triangle  = 180
180 / 18 = 10

largest angle = 10 x 9 = 90

answer
largest angle = 90 degrees