Answer:
The sum is equal to 
Step-by-step explanation:
we know that
The formula to calculate the sum is equal to

In this problem
-----> number of terms
a1 is the first term

an is the last term

substitute

Answer:
x = 3 "1" blocks
Step-by-step explanation:
1,2,9,4,12
hope this helps
2x+18+1-1 works if that's all you want
Answer: 12x-8y
Step-by-step explanation: