Respuesta :

Answer: He made $90 last week.

Assumption :

Let, Luis made $X last week.

He made $72 this week which is 80% of $X that he made last week

⇒ X * 80% = 72

⇒ X * 80/100 = 72

⇒ X = (72 * 100)/80

⇒ X = 90

Therefore, he made $90 last week.

To remember :

While solving this type of problems, be careful to understand which one of last time and current time is not given; just assume that one and input other conditions, the problem will be solved.