How do i find the value of x if a triangle is equilateral?

Part 1 :Using a variable, write an expression that describes the total amount of money earned by both boys at the end of the month.

Let the number of lawns mowed be = x

Earnings of Amar = 20x

Earnings of Sang = 15x

So total earnings are =

Part 2: Amar and Sang mowed 10 lawns each by the end of the month. They need $400 for a summer trip. Do they have enough money for their trip?

Total number of lawns mowed by each are = 10

Amar earned =

Sang earned =

So, total money earned = = $350

No, they don't have enough money for their trip. They are short of $50.