Aramp is being used to unload the back of a truck. the bottom of the ramp is 12 feet from the truck and the top of the ramp is lying on the back of the truck. if the back of the truck is 5 feet high, how long is the ramp?

17 ft

You may recognize the dimensions as belonging to the (5, 12, 13) Pythagorean triple.
   The ramp is 13 ft long.

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In case you haven't memorized that set of right-triangle dimensions, you can figure them out using the Pythagorean theorem.
   (ramp length)² = (bed height)² + (distance from truck)²
   (ramp length)² = (5 ft)² +(12 ft)²
   (ramp length)² = (25 +144) ft² = 169 ft²
Taking the square root, you have
   (ramp length) = √(169 ft²) = 13 ft

21

Step-by-step explanation:

3+(a+4)(8-b)

3+(5+4)(8-6)

3+(9)(2)

3+18

21