Question

Math. :)

Answer 1

This is one-step equation.
$W+2.1=5.4 \\ W+2.1-2.1=5.4-2.1 \\ W=3.3 \\ CHECK- \\ 3.3+2.1=5.4$

Answer 2

$\sf~W+2.1=5.4$

Subtract 2.1 to both sides:

$\sf~W=3.3$