The formula to find a certain number in an arithmetic sequence is an=a1+d(n-1) where an represents the nth term of the sequence, a1 is the first term of the sequence, and d is the common difference. solve for d

Step-by-step explanation:

We need to do some algebraic manipulation to the formula to get our answer [solving for d]:

Note: we will first use distributive property  a(b+c) = ab + ac

Now,

This is d's expression.

the first option is the answer.