Answer:
7^22
Explanation
Given the expression
7^8 × 7^3 × 7^4 × 7^7
In indices
a^m × a^n = a^{m+n}
The powers are added since the base are the same
We ate going to add all the powers of the expression given since they have the same base which is 7
7^8 × 7^3 × 7^4 × 7^7
= 7^{8+3+4+7}
= 7^22
= 3.91×10^18