Let X = number of minutes.
Plan A = 50 + 0.04X
Plan B = 60 + 0.02X
50 + 0.04X = 60 + 0.02X
Subtract 50 from each side:
0.04X = 10 + 0.02X
Subtract 0.02X from each side:
0.02X = 10
Divide both sides by 0.02
X = 10 / 0.02
X = 500
It will take 500 minutes.
