y = 22x ; where x is the number of necklaces sold and y is the mount of profit.
y = 29x ; where x is the number of necklaces sold and y is the amount of profit.
Xavier will earn an additional $7 if he proceeded in switching to a new type of pendant. The $7 is the difference of $29 and $22 profit.
if x is the amount sold and y is the profit, then the original equation would be y = 22x since originally he was selling them for $22 dollars each. That means that in the equation y = 29x, 29 is the amount of profit per each necklace. From here it's just simple subtraction. New profit - Old profit = How much more earned $29 - $22 = $7 extra earned per necklace. he would save $7.
