Arithmetic sequences increase by the same value in between terms. So term2 - term1 = term3 - term2. Apply that logic to this question and you have an equation in terms of p, then rearrange and solve.
Arithmetic sequences increase by the same value in between terms. So term2 - term1 = term3 - term2. Apply that logic to this question and you have an equation in terms of p, then rearrange and solve.