## Intermediate Algebra for College Students (7th Edition)

$975$
Need to apply the summation formula for the arithmetic sequence, such as: $\sum_{i=1}^{n}A=\dfrac{n}{2}(A_1+A_2)$ We have $\sum_{i=1}^{15}b_i-\sum_{i=1}^{15}a_i=\dfrac{15}{2}[b_1+b_1(15-1)d_2)-(a_1+a_1+(15-1)d_1)$ $=7[3+73-1-55]$ $\sum_{i=1}^{15}b_i-\sum_{i=1}^{15}a_i=975$