Paul bought 9 total shirts for a total length f $72. tee shirts cost $10 and long sleeve shirts cost $7. how many of each type shirt did he buy

X = tee shirts, y = long sleeved shirts

x + y = 9x = 9 - y
10x + 7y = 72

10(9 - y) + 7y = 72
90 - 10y + 7y = 72
-10y + 7y = 72 - 90
-3y = - 18
y = -18/-3
y = 6 <=== 6 long sleeved shirts

x + y = 9
x + 6 = 9
x = 9 - 6
x = 3 <== 3 tee shirts

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