The magnitude of the vector is √(7^2+12^2)=√(49+144)=√193
The direction is α=arctan(y/x)=arctan(12/-7)≈-59.74 however this is relative to the negative x-axis so we add 180° to get the standard angle...180-59.74=120.26°
So the vector is √193 @ 120.26°
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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