For the first plan:
Joining fee = $150
monthly fee = $10
Cumulative cost in x months = $(150 + 10x)
For second plan:
Joining fee = $50
monthly fee = $30
Cumulative cost in x months = $(50 + 30x)
Let the cumulative costs of both plan are equal after x months.
![50 + 30x = 150 + 10x \\ \\ 30x - 10x = 150 - 50 \\ \\ 20x = 100 \\ \\ x = (100)/(20) = 5 \: months](https://img.qammunity.org/2019/formulas/mathematics/middle-school/dqpkt6o4hpjxsiwye3ahqgvnkw56vpai5a.png)
On 5th month, the cumulative costs will be equal.
Cost = 50 + 5×30 = 50 + 150 = $200