Please help me solve from 16 to 20

16. Write down all steps to solve following problems Marks 4 a. 500 decreased by 40% is what number? b. 150 increased by 20% is what number? 17. Finding Rate of Increase or Decrease Marks 6 a. In March John worked a total of 40 hours, in April he worked 50 hours by what percentage did John's working hours increase in April? b. The phone manufacturer lowers the price from $500 to $475. By what percentage has the price decreased? c. A pair of shoes went from $18 to $24, what is the percentage change? 18. Solve following linear equations Marks 4 a.8x10=2x+16 b.3x+2x+7x=36 19. 5 (3x 4) = 3(6- 2x) Marks 2 20. There are 900 students in a school. If the number of girls is 200 more than the boys, how many boys are there in the school? Marks 2