Make 'a' the subject of the formula: p = (3a + 5) / (4 - a)

Firstly, multiply the whole equation by (4 - a) to cancel out the denominator, so the equation becomes: p(4 - a) = (3a + 5). Then expand the brackets: 4p - ap = 3a +5. Then rearrange the equation to: 4p - 5 = 3a + ap, so you can factorise 'a' into brackets: 4p - 5 = a(3 + p). Now make 'a' the subject by dividing (4p - 5) by (3 + p), so your equation becomes: a = (4p - 5) / (3 + p).