Remark
This requires some sort of constant that each of the ratio members is multiplied by.
Call the constant x
Equation
2x + 3x + 7x = 90 Add the left hand side
Solution
12x = 90 Divide by 13
x = 90 /12
x = 7,5
Answer
2x = 2 * 7.5
2x = 15
3x = 22.5
7x = 52.5
Sum = 90 as it should be
