Question:
The relationship between t and r is expressed by the equation 2t+3r+6 = 0. If r increases by 4, which of the following statements about t must be true?
Answer:
The value of t is reduced by 6 when the value of r is increased by 4
Explanation:
Given

Required
What happens when r is increased by 4
-------- Equation 1
Subtract 2t from both sides

--- Equation 2
When r is increased by 4, equation 1 becomes
Note that the increment of r also affects the value of t; hence, the new value of t is represented by T
Open bracket
Rearrange

Substitutr -2t for 3r + 6 [From equation 2]

Make T the subject of formula

Divide both sides by 2


This means that the value of t is reduced by 6 when the value of r is increased by 4