Solution: 2/7× 1/3 = 1/2× (4-x)

2/2 1 = 2-X/2

2-(2/2 1) = X/2

40/2 1= X/2

X = 2×(40/2 1)

X =3 and 2 1.0 1.

Question 2: 0.8: Fifteen quarters = (5-x): 0.75

Solution: 15 ×(5-x)=0.75×0.8.

( 15/4)×5-( 15/4)X = 3/5

(75/4)-3/5=( 15/4)X

363/20 =( 15/4)X

X =(363/20)÷( 15/4)

X = 4 25 2 1

Question 3: 3, 6, 4 and 8 are all called proportional terms, and (3 and 8) are called external proportional terms. (6,4) An internal term called proportion.

Question 4: If a:b=5:4, then B× 5: (a )× (4). According to the relationship between the ratio and the score, a:b=5:4 can be written as A/B = 5/4, so A/B = 5/4.