Lisa spends part of her year as a member of the gym. She then finds a better deal at another gym, so she cancels her membership with the first gym and spends the rest of the year with the second gym. (12 months total at these gyms.) The membership to the first gym costs $75 per month, while the membership for the second gym cost $50 per month. She ends up spending a total of $775 over the course of the year.

Number of month in first gym = 7

Number of month in second gym = 5

Step-by-step explanation:

Given:

First gym member ship cost = $75 per month

Second gym member ship cost = $50 per month

Total spending = $775

Computation:

Number of month in first gym = a

Number of month in second gym = b

So

a + b = 12eq1

75a + 50b = 775 eq2

From eq 1 and 2

a = 7 month

b = 5 month

Number of month in first gym = 7

Number of month in second gym = 5

hello from mrbilldoesmath!

answer:

a(n) - a(n-1) -3

discussion:

this ones a bit interesting. given a(n) = 5 - 3n consider this:

a(n-1) = 5 - 3(n-1)

          = (5 - 3n) + 3             => but a(n) = 5 - 3n, the first term

          = a(n)   + 3                 => subtract 3 from both sides

a(n-1) -3 = a(n)  

or

a(n) - a(n-1) -3

you,

mrb