Ihave tried a couple of equation but none of them worked. .

Let's start with the information we know. 

Aiden gets $85 a month
Over 7 months, he has saved (85*7 = 595) $595
He will need to have $1955 for the laptop

1955 -

Now figure out how many months he will have to spend to get 1955 - the 595 he already has (1360 is what that comes out to.) 1360 (The total he will need) / 85 (The number you get a month)

That equals 16.
It will take Aiden at his current rate of income, 16 months to save for his new computer. 

--Something to remember--

If the number you come out with is a decimal, I.E. 16.2, you will need to round up to the nearest whole number unless the equation specify's. In this case, instead of 16.2 it would be 17 months

Ai just took the test