Write the given expression

Identify the expression to evaluate using the standard order of operations: $12.5 + 4.2 imes 3 - 8.4 / 2$.

$12.5 + 4.2 imes 3 - \frac{8.4}{2}$

Perform Multiplication and Division

Calculate the multiplication part ($4.2 imes 3 = 12.6$) and the division part ($8.4 / 2 = 4.2$).

$4.2 imes 3 = 12.6, \quad \frac{8.4}{2} = 4.2$

Substitute values back into the expression

Replace the multiplication and division results into the expression: $12.5 + 12.6 - 4.2$.

$12.5 + 12.6 - 4.2$

Perform Addition and Subtraction

Add $12.5$ and $12.6$ to get $25.1$, then subtract $4.2$ to arrive at the final result of $20.9$.

$25.1 - 4.2 = 20.9$