Acandle is 7 in. tall after burning for 1 h. the same candle is 5 1/2 in. tall after burning for 4 h. write a linear equation to model the height y after burning x hours

You are given two points on the line:
.. (1, 7) and (4, 5.5)

You can use the 2-point form of the equation for a line.
.. y = (y2-y1)/(x2-x1)*(x -x1) +y1
.. y = (5.5 -7)/(4 -1)*(x -1) +7
.. y = -0.5x +7.5

Your linear equation is y = -0.5x +7.5

Well if you have 20 bats you probably want 20 balls? you don’t have enough context to answer the question.