-3y + 12 = -48
what number is the y

Fraction = 3/14
% = 21.428%

Explanation:
First, we will get the mixed forms of the length for simplicity:
length of section = 1 1/4 miles = 5/4 miles
length of circuit = 5 5/6 miles = 35/6 miles
Then, to get the fraction that the straight section represents from the whole circuit, we will follow these steps:
1- Divide the length of the section by the total length of the circuit
2- Multiply the quotient by 100 to get the percentage (if needed)
Therefore:
Fraction = (5/4) / (35/6) = 3/14
% the the section represents from the circuit = (3/14) * 100 = 21.428%

Hope this helps :)