Please help and don't say soothing random to get points

The students at jefferson middle school are raising money for a charity by selling t-shirts and hats. the number of t-shirts sold was 3 times the number of hats. the profit was $5 for each t-shirt sold and $2.50 for each hat sold. the students raised $840 for the charity. they used the system below to analyze their success and found the solution to be (144, 48). 5x+2.50y=840 x=3y how much did they earn from t-shirt sales?

Me because i don't understand how to do it.: )

Suppose that circtes a and b have a central angle measuring 100. additionally, the measure of the sector for circle a is 10 m2 and for circle b is 40 m2 if the radius of circle a is 6 m, what is the radius of circle b?