Okay this is the basic when there is a - + + = -
It is 1595. Put it on excel so you can better have an overview how it is done. You need 5 columns, column A-E. On column A, put 1 to 5 in rows 1 to 5. On column C, put the answers: 2, 7, 26, 101 and 400. On column D, put number 3 in all 5 rows. Back on column B, insert =sum(C1-A1) on row 1 and copy till row 5. On column E, insert =sum(B1+C1*D1) on row 1 and copy till row 5 and you will get 1595 at the end.
The answers are boxed the rest of it is just the work in case you want to know how to do it.
Maybe try add it then takeaway most of it
The equation can be made by:
Letting x be the price of each tshirt sold
Y be the cost of washing cars
So the equation 1:
292.50 = 15x + 12y
Then the equation 2 is for this week:
<span>747.50 = 45x + 10y</span>