Can u pl me with these question in the pic and show how to wrok them out plzz

18) 
The Last case is 252 because 28 * 9 = 252. 
Second Case is 9 because 8*9 = 72, and 252 - 72 = 180, then you divide 180 over 20, and you get 9.
So, 28 * 9 = 20 * 9 + 8 * 9 = 252

19)
in Math, when they say "of", it means you need to multiply, so you get:

do it on the calculator and you get 56.

20)
To add fractions, they need to have the same denominator. Since here they got the same (10), you get:




Hope this Helps! :D