It's a lot like solving equations.
3b-7 < 32
Add 7 to each side.
3b < 39
Divide by 3 on each side.
b < 13
Hope this helps :)
Answer:
Unit rate of change = -4.2°F/hour
Step-by-step explanation:
Assuming a constant rate of change, a relationship between the change of temperature as a function of time (in hours) can be described as follows:

There is a temperature drop from 12pm to 5pm, which explains the rate of change being negative. This rate means that at every hour that goes by, the temperature drops by 4.2 degrees.
You can solve the problem this way:
Your money is increading $6 a week while sister's is decreasing $7 a week (because she isn't saving any and is spending $7 of what she has weekly)
Your money each additional week vs sister''s:
80/145 (Week 0)
86/138 (Week 1)
92/131 (Week 2)
98/124 (Week 3)
104/117 (Week 4)
110/110 (Week 5) The amounts are the same in 5 weeks.