Answer
$151_{\text{seven}}$
Work Step by Step
The place values of base seven are: $,,,, 7^3, 7^2, 7^1, 1$.
The place values that are less than or equal to $85$ are $7^2$, $7^1$, and $1$
Divide $85$ by $7^2$ or $49$ to obtain:
$85 \div 49 = 1$ remainder $36$
Divide the remainder $36$ by $7^1$ or $7$ to obtain:
$36 \div 7 = 5$ remainder $1$
Divide the remainder $1$ by $1$ to obtain:
$1 \div 1 = 1$ remainder $0$
Thus,
$85=(1 \times 7^2) + (5 \times 7^1) + (1 \times 1)
\\85=151_{\text{seven}}$
