Mn giúp e câu này vs ạ em cảm ơn

Present age of man is 45 years, 5 years back his age was 4 times age of his son what is present age of his son?

Using only the digits 5, 6, 7, 8, how many different three digit numbers can be formed if no digit is repeated in a number?

Urgent need asap △abc is similar to △xyz. also, side ab measures 6 cm, side bc measures 18 cm, and side xy measures 12 cm. what is the measure of side yz ? enter your answer in the box.