### Home > AC > Chapter 4 > Lesson 4.2.2 > Problem4-84

4-84.

In Spring, the daily high temperature in Boulder, Colorado rises about $\frac{1}{3}$ degree per day. On Friday, May 2, the temperature reached $74°$. Predict when the temperature will reach $90°$.

Using the equation $y = mx + b$, put the word problem into equation form.

What is the growth rate?

What is the starting point?

What is the desired temperature?

Now, solve for $x$.

$\frac{1}{3}x$

$\frac{1}{3}x + 74$

$\frac{1}{3}x+74\ =\ 90$

$48$ days later
(Thursday, June 19).