BODMAS is a useful acronym that lets you know which order to solve mathematical problems (or sums). It's important that you follow the rules of BODMAS as without it your answers can be wrong.
The BODMAS acronym is for:
Example: 42÷2+1×3−22
42÷2+1×3−22
=21+3×1−22 ( Using BODMAS rule, First solve, 42÷2=21)
=21+3−22 [Then multipy]
=24−22=2 [Then, add and subtract]