An expression is a mathematical phrase with no equals sign, such as $2n - 3$ for "3 less than double a number". It has a value depending on $n$, but there's nothing to solve. An equation contains an equals sign and asserts two expressions are equal, such as $8y - 66 = 2y$, which can be solved for $y$.

Learn the keyword-to-operation links: "more than / sum / total" → add; "less than / difference" → subtract; "times / product / lots of" → multiply (write the number before the letter, e.g. $3n$ not $n3$, to avoid confusion with $n^3$); "shared between / divided by" → divide.

Work through the sentence in the order the operations are described, but add brackets whenever a single operation must apply to an entire previous result.

• "$t$ add 2, then multiplied by 5" → the addition must happen first and the whole result gets multiplied: $5(t+2)$.
• Without brackets, $5t+2$ would mean "multiply by 5, then add 2" — a different instruction entirely.

Identify the unknown, express every other quantity in terms of it, then combine and simplify as instructed.

Example: a rectangle has length $3x+2$ and width $x-1$. Find its perimeter in simplest form.

Grouping the $x$-terms ($3x+x+3x+x=8x$) and the numbers ($2-1+2-1=2$):

A child's cinema ticket costs $\pounds x$. An adult's ticket costs $\pounds 5$ more than a child's.

(a) Write an expression for the price of an adult's ticket.

(b) Write an expression, in its simplest form, for the cost of one adult's ticket and two child's tickets.

(a) "£5 more than $x$" translates directly: $x+5$.

(b) One adult plus two children: $(x+5) + 2x$. Collecting like terms: $3x + 5$.

Before finalising an answer, re-read the question's exact final phrase. Examiner reports for this topic repeatedly note that students correctly translate most of a scenario but then answer, say, "the total number of boxes" when the question asked for "the total number of items inside the boxes". Underlining the command phrase on first reading — and checking your final expression against it — catches this reliably.