TeX source:

\begin{aligned} 2 \times 10 &=2 \times 2 \times \mathrm{Q}_{\text {burgers }}+2 \times 0.5 \times \mathrm{Q}_{\text {bus tickets }} \\ 20 &=4 \times \mathrm{Q}_{\text {burgers }}+1 \times \mathrm{Q}_{\text {bus tickets }} \end{aligned}