Student scores

Dorka had a total of 22 marks in her student book. She had three times less than three ones. She had only two doubles. How many units did Dorka have in the student's book, and how many threes?

Final Answer:

a =  5
c =  15

Step-by-step explanation:

a+c = 22-2
a=c/3

a+c = 20
3a-c = 0

Pivot: Row 1 ↔ Row 2
3a-c = 0
a+c = 20

Row 2 - 1/3 · Row 1 → Row 2
3a-c = 0
1.33c = 20


c = 20/1.33333333 = 15
a = 0+c/3 = 0+15/3 = 5

a = 5
c = 15

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