Exercise 42 Page 9

Let x represent the change in temperature. Since the beginning temperature is 20^(∘), subtracting x from 20 gives the ending temperature of - 5^(∘). 20 - x = - 5 Solving this equation for x gives the change in temperature.

20 - x = - 5

SubEqn

LHS-20=RHS-20

- x = - 25

DivEqn

.LHS /- 1.=.RHS /- 1.

x = 25

The solution x=25 means that the temperature decreases 25^(∘).