a + b = 10 pounds
rewrie as:
a = 10 pounds - b
0.75a + 0.50 b = $6.00
replace a with the above equation:
0.75(10-b) +0.50b = 6.00
distribute the(10-b):
7.50 - 0.75b + 0.50b = 6.00
combine like terms:
7.50-0.25b = 6.00
subtract 7.50 from each side:
-0.25b = -1.50
divide both sides by 0.25 to find b
b = -1.50 / -0.25
b = 6
she bought 6 pounds of bananas and 4 pounds of apples