Solve this system by substitution. y = 6x + 12 y = -4X - 18 *Remember to write your answer as a coordinate point (x, y).​

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?

I’m still confused on how to work the percentages

3x = 729 solve for x plz . it's urgent. will mark