
Perimeter of a triangle = sum of measures of each side ;


Looks like you just evaluated the summand for the given value of

, whereas the question is asking you to find the value of the sum for the first

terms.
Let

. Then

is the

th partial sum.

happens to be the first term in the series, which is why that box is marked correct:

But the next partial sum is not correct:

and this is not the same notion as the second term (which indeed is 0.75) in the series.
Just look at the line and see how many times it goes up it is just like rise over run it is simple
3(5j+2)=2(3j-6) do distributed to remove parenthesis 15j+6=6j-3 . Then move all j to left side and the second term to right side 15j-6j=-3-6. Now solve both sides 9j= -9. Now divide both sides by 9 to get j alone to j = -1
That is false, because if you were to use my ATM then it will charge you 3%