The volume for 3 boxes of detergent is 864 inches
Volume= length X width X hight
V=12X8X3
V=288
V=864 (288 times 3 for 3 boxes)
10a + 8b = 230
a + b = (2 + 2 + 13 + 10)...a + b = 27 (this is the number of gifts to buy)
a = 27 - b
10(27 - b) + 8b = 230
270 - 10b + 8b = 230
-10b + 8b = 230 - 270
-2b = -40
b = -40/-2
b = 20 <=== she bought 20 eight dollar gifts
a = 27 - b
a = 27 - 20
a = 7 <=== she bought 7 ten dollar gifts