P1.1.6 - Solve simultaneous equations

Solve simultaneous equations; analytical solution by substitution.

Use solve simultaneous equations to connect the rule to the data and decision in the question.

This matters because solve simultaneous equations determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply solve simultaneous equations to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: use the formula and units given in the question, show the substitution and interpret the result; the calculation alone is not the conclusion.