Follow BIDMAS, from top to bottom:

The same signs apply to division. Subtracting a negative is the same as adding: $a - (-b) = a + b$.

Example: $8 - (-3) = 8 + 3 = 11$ — the two minus signs combine into a plus.

Example: work out $24 - 2 \times (5 + 3^2)$.

1. Inside the brackets, do the index first: $3^2 = 9$.
2. Finish the bracket: $5 + 9 = 14$, leaving $24 - 2 \times 14$.
3. Multiply before subtracting: $2 \times 14 = 28$.
4. Subtract: $24 - 28 = -4$.

Example: evaluate $-1\frac{1}{4} + \dfrac{5}{6} \times \dfrac{3}{5}$.

1. Multiplication comes first. Cancel common factors before multiplying:

1. Convert the mixed number: $-1\frac{1}{4} = -\frac{5}{4}$.
2. Find a common denominator ($4$) and add:

Treat a rise in temperature as addition and a fall as subtraction, keeping careful track of the sign of the starting value.

Example: the temperature at midnight is $-6°\text{C}$. By midday it has risen by $9°\text{C}$, and by midnight the following day it has fallen by $14°\text{C}$ from its midday value. Find the temperature at midnight the following day.

1. Rise from midnight to midday: $-6 + 9 = 3°\text{C}$.
2. Fall from midday to the next midnight: $3 - 14 = -11°\text{C}$.
3. Final temperature: $-11°\text{C}$.

• Ignoring priority and working strictly left to right, e.g. treating $6 + 4 \times 2$ as $(6+4)\times 2 = 20$ instead of $6 + 8 = 14$.
• Assuming addition always beats subtraction because of the order of letters in BIDMAS — they're equal priority, so work left to right.
• Dropping a negative sign when subtracting a negative number, e.g. rushing $8-(-3)$ into $5$ instead of $11$.