Solving a word problem with three unknowns using a linear equation

Question

Mary, Henry and Chang served a total of 105 orders Monday at the school cafeteria. Mary served 9 more orders than Henry. Chang served 2 times as many orders as Henry. How many orders did they each serve?

Answer 1

Let x = number of orders served by Henry. Then x+9 = number of orders served by Mary and 2x = number of orders served by Chang.

x + (x+9) + 2x = 105

Solve for x.