a = hours worked by the first mechanic
b = hours worked by the second mechanic.
since the first mechanic charges $55 per hour, then for "a" hours that'd be a total of 55*a or 55a, likewise, for the second mechanic that'd be a total charge of 80*b or 80b.
we know all hours combined are 15, so then a + b = 15.
we also know that all charges combined are $950, so 55a + 80b = 950.

Use combine like terms the answer is 7r^2-r-1
Answer:
-2.4
Step-by-step explanation:
Answer:
39,900
Step-by-step explanation:
original cost 100*399 = 39,900
Answer:
A
Step-by-step explanation:
That is the answer to the question.