How to write an equivalent expression for n times a using only addition

Henry is an avid reader, he devours 90 pages in half an hour how many pages has henry read per minute?

Given that abcd is a rhombus, what is the value of x?

Aparticular telephone number is used to receive both voice calls and fax messages. suppose that 25% of the incoming calls involve fax messages, and consider a sample of 25 incoming calls. (a) what is the expected number of calls among the 25 that involve a fax message?