The temperature rises by 18°F. What is the rise on the Celsius scale?

180 divisions on the Fahrenheit scale = 100 divisions on Celsius scale

1 division on Fahrenheit scale = $\dfrac{\text{100}}{\text{180}}$ divisions on Celsius scale

18 divisions on Fahrenheit scale = $\dfrac{\text{100}}{\text{180}}$ x 18 =10 divisions on Celsius scale

So the corresponding rise on the Celsius scale = 10°C.