Why can’t we add 5x and 11 together

Fanny mendelssohn manages all the magazines and paperback books at a local grocery store. she prices many paperbacks to sell at $7.99. the cost to the store is $5.29. what is the markup rate on a paperback book, based on its cost?

Write an equation in slope intercept form of the line passes through the given point and is parallel to the graph of the given equation (0,0); y=3/8 x+2

Find the equation of a line whose slope is 2/5 and y- intercept is 2.write your answer in the form 1) ax+by+c=02) x/a+y/b=1