HELP ME PLEASE

24d=12
What is d

-12c=12
What is c

Find the solution of this system of equation -7x+y=-20 9x-3y=36

If 7x=9y, y/z = 7/5 , then x/z = (a) 2/7 (b) 7/9 (c) 9/5 (d) 9/7 (e) 5/9

Which verbal expression best describes the algebraic expression 3x ÷ 5? the quotient of three times some number and five the product of some number and five divided by three the quotient of three and some number times five the sum of three and some number divided by five