First you have to remember that to find a percentage you can multiply a number by the percentage's decimal form, for example 40% of 100 would be .40 * 100.
Anyways, 24*.40 =9.6.
To find the percentage however, you must divide 24/40 which equals 0.6, which is equal to the percentage 60%.
To find the third question, you must multiply 24 by 2.5 (0.4 * 2.5 = 1) and you should get 60.
The last question you may have made a typo on, you repeated the first question.