It should be Jia Xuan instead of Suzana in the first sentence.
Notice that the total number of cupcakes is unchanged since no cupcakes were given away to others.
At first, Richita has 2 units ⬛⬛, Jia Xuan has 1 unit ⬛
Total : 3 units ⬛⬛⬛
After the giving, Richita has 5 parts ■■■■■, Jia Xuan has 1 part ■
Total : 6 parts ■■■■■■
Since the total is unchanged, we can say that 6 parts = 3 units (■■■■■■ = ⬛⬛⬛)
This means that 2 parts = 1 unit (■■ = ⬛)
So we can rewrite their number of cupcakes at first as :
Richita has 4 parts at first ■■■■, Jia Xuan has 2 parts ■■ at first.
Since Jia Xuan is left with 1 part ■ at the end, she must have given 1 part to Richita (■■ - ■ = ■)
Since she gave 20 cupcakes to Richita, then this means that 1 part ■ = 20 cupcakes.
a)Number of cupcakes Jia Xuan had at first = 2 parts = 2 × 20 = 40
b) Number of cupcakes Richita has after Jia Xuan gave her = 5 parts ■■■■■
= 5 × 20 = 100