1, two thirds 1: 5 2=X: one third.

solve

1/2:2/5=X: 1/3

(2/5)×X=( 1/2)×( 1/3)

X=( 1/2)×( 1/3)÷(2/5)

= 1/6×5/2

=5/ 12

2.8/x =1/3: 0 of 65438+4.

solve

8:X= 1/3: 1/4

( 1/3)×X=( 1/4)×8

X=( 1/4)×8×3/ 1

=6

3.0.5: x = one quarter: two fifths.

solve

0.5:X= 1/4:2/5

( 1/4)×X=(2/5)×0.5

X=(2/5)×0.5×4

=0.8