(a)[4]
A mass of $4$ cards together with $3$ envelopes is $85\,g$. A mass of $2$ cards together with $5$ envelopes is $67\,g$. Set up a pair of simultaneous equations and solve them to determine the mass of one card and the mass of one envelope.
(b)[1]
Factorise the expression $x^2 - 25$.
(c)[3]
Rearrange the formula $r = \frac{2t}{t - 5}$ so that $t$ is the subject.
(d)[3]
Express $\frac{4}{x - 5} - \frac{3}{2x + 1}$ as a single fraction in its simplest form: