Answer:
82
Step-by-step explanation:
The sum resolves to ...
13 + 18 + 23 + 28 = 82
_____
for n=2, the term is 5·2 +3 = 10+3 = 13
The coefficient of n is 5, so you know the next term will be 5 more than this:
for n=3, the term is 5·3 +3 = 15+3 = 18
Additional terms are each 5 more than the one before. Since there are so few terms, you can add them up directly as quickly as you can use any other formula. For a longer series, you might find the average term (here, 41/2), then multiply by the number of terms (here, 4). The result is the sum of the series:
4·(41/2) = 82
