Write an equation for each of these and solve it to find the value of the unknown number:

a) i think of a number, i multiply it by 5 then add 5. the answer is 20

b) i think of a number, i divide it by 5 then subtract 5. the answer is 4

a) a *5+5= 20

5a + 5 = 20

5a = 20 - 5

5a = 15

a = 15/5

a = 3

b) b/5 - 5 = 4

b/5 = 4 + 5

b/5 = 9

b =9*5

b = 45

(sin 42)/31. = sinx)/37

sinx = 37 (sin42)/31

= 37× 0.66/31 = 0.787

x= 51.9

other angle opposite to y = 180-51.9-42

= 180- 93.9 =86.1

so

sin42)/31 = sin 86.1)/y

0.021 = 0.997 /y

y= 0.997/0.021 =47.47

example 2 – simplify: step 1: completely factor both the numerators and denominators of all fractions. step 2: change the division sign to a multiplication sign and flip (or reciprocate) the fraction after the division sign; essential you need to multiply by the reciprocal. step 3 : cancel or reduce the fractions.