Answer
$103_{\text{four}}$
Work Step by Step
The place values of base four are: $,,,, 4^3, 4^2, 4^1, 1$.
The place value that are less than or equal to $19$ are $4^2$, $4^1$, and $1$
Divide $19$ by $4^2$ or $16$ to obtain:
$19 \div 416 = 1$ remainder $3$
Divide the remainder $3$ by $4$ to obtain:
$3 \div 4 = 0$ remainder $3$
Divide the remainder $3$ by $1$ to obtain:
$3 \div 1 = 3$ remainder $0$
Thus,
$19=(1 \times 4^2) + (0 \times 4^1) + (3 \times 1)
\\19=103_{\text{four}}$
