assalamualaikum warohmatullahii WABARAKATUH guys bantu jawab nya

a. 4/2 : 10/ x
4x = 2 kali 10
4x = 20
x = 20 : 4
x = 5

b. 10/20 : 4/y
10y = 20 kali 4
10y = 80
y = 80 : 10
y = 8

semoga benar dan bermanfaat