Analyze Mr Johnson's work and identify his
mistake.

Mr Johnson is also comparing the two mobile
phone data plans. Talk First charges $20 plus $5
per GB of data, while Mobile Plus charges $30
plus $3 per GB of data At what amount of GB use
will the cost of the two data plans be the same?

Mr Johnson wrote this equation for the scenario
1. d= amount of data used (GB)
2. Talk First Mobile Plus
3. 20d+5=30d+3

In step 1 his variable should be c
representing company
In step 2 his translated equation should be
Talk First + Mobile Plus = Total
Money
In step 3 he multiplied the variable by the
base monthly cost nstead of by the
cost per GB