8x^2 - 16x - 15 = 0
x = [ -(-16) +/- sqrt((-16)^2 - 4*8*-15) / ] 2*8
= 2.696, -0.696
-4 and -5
because to get 16 to 12 you have to subtract 4 but it wants you to add so you put a negative sign infront of it.
and a negative multiply by a negative equals a positive so -3×-5=15
Bill = $25.85
Tips = 15% x $25.85 = $3.88
Tax = 6.25% x $25.85 = $1.62
Total amount = $25.85 + $3.88 + $1.62 = $31.35
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Answer: He will spend $31.35 in total.
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