Cindy decided to shop online. She was buying books ($6 each) and candles ($4 each). She bought 15 items and spent $78. How many books did she buy?

9 books

Step-by-step explanation:

78=b(6)+c(4)

78=9(6)+6(4)

78=54+24

78=78-True

5=812a+9+3

step 1: simplify both sides of the equation.

5=812a+9+3

5=(812a)+(9+3)(combine like terms)

5=812a+12

5=812a+12

step 2: flip the equation.

812a+12=5

step 3: subtract 12 from both sides.

812a+12−12=5−12

812a=−7

step 4: divide both sides by 812.

812a /812 = -7/812

a= -1/116

so the answer is

a=   -1/116