If (a,-7) is a solution to the equation 8a+3b=3, what is a?

8a=-3(-7)-5
8a=21 -5=16
A=2
Substitue the value -7 for the b in the equation 

B=-7
8a+3(-7)=3
8a+(-21)=3
8a-21=3
8a=24

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Answer for 2: his profit would be $2.88 explanation: you have to first multiply 72 and 0.12 together to get $8.64 once you do that you know how much money the shopkeeper made from selling the candy bars individually. so you have to do 8.64-5.76=2.88 hope that ; )answer for 3: yeah i’m sorry i have no idea what number 3 is. i’m sorry i couldn’t with that.