Justin gave ¹₉ of his marbles to Brandon, ¹₈ of his remaining marbles to Glen and ¹₅ of the rest of his marbles to Luis. He then had 28 marbles left. How many marbles had he at first?
Fraction of the rest of the marbles that Justin had left after giving to Brandon, Glen and Luis
= 1 - ¹₅
= ⁴₅

⁴₅ of the rest of the marbles that Justin had left = 28
¹₅ of the rest of the marbles that Justin had left = 28 ÷ 4 = 7
⁵₅ of the rest of the marbles that Justin had left = 5 x 7 = 35

Fraction of his remaining marbles that Justin had left after giving to Brandon and Glen
= 1 - ¹₈
= ⁷₈

⁷₈ of his remaining marbles that Justin had left = 35
¹₈ of his remaining marbles that Justin had left = 35 ÷ 7 = 5
⁸₈ of his remaining marbles that Justin had left = 8 x 5 = 40

Fraction of his remaining marbles that Justin had left after giving to Brandon
= 1 - ¹₉
= ⁸₉

⁸₉ of the marbles that Justin had left = 40
¹₉ of the marbles that Justin had left = 40 ÷ 8 = 5
⁹₉ of the marbles that Justin had left = 9 x 5 = 45

Number of marbles that Justin had at first = 45

Answer(s): 45