Exercise 4.
a) Since Profit (P) is (equal to) Revenue (R) minus Expenses (E) we can write P = R - E and we know that E = $10 million. So P = R - 10
b) appling the fomula written above, we put P = 25 - 10 = $15 million
c) Let's use the inverse formula. From P = R - E we need R, so move R to the left of equal with changed sign and move P to the right of equal with changed sign. We get - R = - P - E so, make it positive... R = P + E
R = 10 + 5 = $15 million
Exercise 5
a) substitute 15 to x... 3.5 * 15 = y
y = 52.5
b) substitute 144 to y
3.5x = 144 and divide both for 3.5 to find x
3.5x/3.5 = 144/3.5 -> x = 144/3.5 circa 41.1
Exercise 6
a) z = -12 * (-7) -> z = 84
b) 108 = -12x -> 12x = -108 -> 12x/12 = -108/12 -> x = -9
Exercise 7
a) y = 15.3 * (-13) -> y = 198.9
b) 15.3x = 351.9 -> 15.3x/15.3 = 351.9/15.3 -> x = 23
Exercise 8
a) y = -11 + 5 -> y = -6
b) 17 = x + 5 -> - x = -17 + 5 -> x = 17 - 5 -> x = 12
