3. If you add -10 to 4 times the mystery number you get O. What is the Mystery Number?

4. The Links phone company charges has a free smartphone (y-intercept : O) but $60 per month
(rate of change).

The Connections phone company charges S300 for the smartphone (y-intercept) and s40 per
month (rate of change).

a. Write an equation in slope intercept form for each company. (y : mx + b)

b. Write an equation to find out how many months each company will take to get to a cost of
S900 total.
(re-write each equation, but replace the y with 900) c. SOLVE each equation. SHOW each step. ​