Answer:
20 mph
Step-by-step explanation:
The ratio of Alfonso's speed with the wind to his speed against the wind is ...
(x +5)/(x -5) = 75/45 . . . . where x is his speed with no wind
Multiplying by 3(x-5), we get ...
3(x +5) = 5(x -5)
40 = 2x . . . . eliminate parentheses, add 25-3x
20 = x . . . . . divide by 2
Alfonso's speed with no wind is 20 miles per hour.