Step-by-step explanation:
Let there be x blue ribbons
[tex] \therefore \: \frac{1}{5} + \frac{7}{15} + x = 36 \\ \therefore \: \frac{1 \times 3}{5 \times 3} + \frac{7}{15} + x = 36 \\ \therefore \: \frac{3}{15} + \frac{7}{15} + x = 36 \\ \therefore \: \frac{3 + 7}{15} + x = 36 \\ \therefore \: \frac{10}{15} + x = 36 \\ \therefore \: x = 36 - \frac{10}{15} \\ \therefore \: x = \frac{36 \times 15 - 10}{15} \\ \therefore \: x = \frac{540 - 10}{15} \\ \therefore \: x = \frac{530}{15} \\ \therefore \: x = 35\frac{5}{15} \\ \\ \therefore \: x = 35\frac{1}{3} \: are \: blue. \\ [/tex]
