Percent increase and decrease

A percent increase asks for a new total: the original price plus the raise. The raise itself is 20% of the original, not 20% of nothing. So the plan is two moves: find 20% of $50, which is $10, then add it to the original price. The percent never replaces the price; it only tells you how much extra to add.

Zara's mistake was stopping after the first move. Her $10 was the size of the increase, the part that gets added. A jacket that was $50 and goes up in price cannot still cost $10 afterwards, and that quick sanity check is a good habit to apply every time. Asking whether the answer is plausible would have caught the error before it was submitted.

The fix is one clean comparison: original plus change equals new price. Here $50 + $10 = $60. The percent amount is always found against the original amount, because the percent describes a piece of that original, and then that piece is added or subtracted. One sentence summarizes the whole job: find the piece, then move it. Write the original price next to the percent, and the add or subtract choice becomes obvious.

Check the answer by reversing: a $60 jacket dropped back down by the same $10 would lose 10/60, roughly 16.7%, not 20%. That shows why you never take the percent off the new price. The reverse check confirms that $60 is right for this problem, and the whole percent story has a single logical spine. Original, change, result: those three numbers tell the whole story.