Answer
21
Work Step by Step
$16+9\div3\times4-7\rightarrow$ PEMDOS determines order of operation, divide
=$16+3\times4-7\rightarrow$ PEMDOS determines order of operation, multiply
=$16+12-7\rightarrow$ PEMDOS determines order of operation, add
=$28-7\rightarrow$ PEMDOS determines order of operation, subtract
$21$