Step-by-step explanation:

1.

a. Mathematical Sentence.

1/2 × 6/8 = N

b. Solution.

1/2 × 6/8 = (1×6)/(2×8) = 6/16 = 3/8

c. Final answer.

The fraction of the tank of gas he uses is 3/8.

2.

a. Mathematical Sentence.

2/3 × 15/1 = N

b. Solution.

2/3 × 15/1 = (2×15)/(3×1) = 30/3 = 10

c. Final answer.

10 of the prizes are for relay winners.

3.

a. Mathematical Sentence.

30 - 2/5 × 30/1 = N

b. Solution.

30 - (2×30)/(5×1) = 30 - 60/5 = 30 - 12 = 18

c. Final answer.

18 wore their P.E. uniform.