Step-by-step explanation:
a. (3 - 2/3) ÷ (4/3 x 7)
= [(3 x 3) / (1 x 3) - 2/3] ÷ 28/3
= (9/3 - 2/3) ÷ 28/3
= 7/3 x 3/28
= 21/84
= (21 x 1) / (21 x 4)
= 1/4
b. 2/3 ÷ 5/6 - 2/5
= 2/3 x 6/5 - 2/5
= 12/15 - 2/5
= (3 x 4) / (3 x 5) - 2/5
= 4/5 - 2/5
= 2/5
c. (- 3/4 + 1/2) ÷ (2/5 - 5/2)
= [- 3/4 + (1 x 12) / (2 x 2)] ÷ [(2 x 2) / (5 x 2) - (5 x 5) / (2 x 5)]
= (- 3/4 + 12/4) ÷ (4/10 - 25/10)
= 9/4 ÷ (- 21/10)
= 9/4 x - 10/21
= - 90/84
= (6 x - 15) / (6 x 14)
= - 15/14.
If you have any doubt, then you can ask me in the comments.
Percentage of milk PM
Liters of milk LM
Liters of water W
Total number of liters TL
W/100*PM = LM
W+LM =TL
Proof
1 liter / 100 = 10 milliliters
10 ml * 20 = 200 milliliters
200 ml + 1000 ml = 1200 ml
1.2 liters is the total amount of liters.

First see what 4 could go by and the answer closest to 18 that is not more than the answer is the first number of the answer.
4×1=4
4×2=8
4×3=12
4×4=16
In this case 4 is the first number of the answer because if you fo 4 by 5 it equals 20 , which is more than the answer
4×5=20
after that , you subtract the answer, 18 minus 16 which is 2 because nothing times 4 equals 2
So the remainder is 2/4 or .50
If you have any questions about this please don't hesitate to ask me