How can I subtract 0.3 from 1.2?

Subtracting 0.3 from 1.2 involves a simple process. Start by aligning the decimal points and fill in any missing place values with zero. Then, subtract each place value starting from the right.

The calculation would look something like this in column form:

[ \begin{array}{c} 1.2 \ -0.3 \ \hline 0.9 \end{array} ]

So, the answer is 0.9.

In real-life terms, this means that if you have 1.2 and you spend 0.3, you will have 0.9 left.