I agree with you on this problem. It is A. If that is the final answer, the negative exponent must be flipped in order to be positive. According to the equation, it is not positive so it is not a simpflied polynomial.
Exponents are used as a shorthand notation for repeated multiplication.
Let's say d is the cost of the desk and c is the cost of the chair. We know that:
c + d = 720
and
d = 5 * c
We can substitute d in the first equation with 5 * c to solve for c. c = $120.
That’s the answer because I couldn’t type it out! Hope it helped!