What number belongs in the box to make the equation true?
-0.4 divided by what +0.8 = -1.2
a. -1
b. -0.2
c. 0.2
d. 1

One cell phone plan charges $20 per month plus $0.15 per minute used. a second cell phone plan charges $35 per month plus $0.10 per minute used. write and solve an equation to find the number of minutes you must talk to have the same cost for both calling plans.