Answer:
0.1x+0.04y=4,000
x+y=352
Step-by-step explanation:
Answer:

first create a bracket:

then solve the first bracket:

then open the remaining bracket:

carryout the subtraction operation:

10.99x = 3.99x + 280
7x = 280
x = 40
They must sell 40 T-shirts to break even