Well, you have to do it with the substitution method now it's not easy, it takes some time to get used to it. I'm not really sure how to explain it but if you go on Khan Academy it will show you how to do it.
Answer: 33
Step-by-step explanation: The ratio is 4:7, so the number has to be a multiple of 11, and the multiple of 11 between 24 and 40 is 33.
Use the Pythagoras theorem:-
height = sqrt(5^2 - 3^2 ) = sqrt16 = 4 metres Answer.