1. Substitute the values given in the following formulae to find the value of the unknown variable:
(a) 
when d = 60 km and t = 2 hours 

(b) 
A = l w 
when l = 8 cm and w = 5 cm 
(c) 
when = 3.1 and r = 9 cm 

(d) 
when A = 50 cm^{2} and h = 18 cm 

(e) 
when x = 3 m and y = 4 m 
2. Make the variable shown in brackets, the subject of the following formulae :
(a) 
(y) 

(b) 
P = 2(a + b) 
(a) 
(c) 
2y − 3x = 4 
(y) 
(d) 
(r) 

(e) 
v = u + 2as 
(s) 
(f) 
(r) 

(g) 
(r) 
3. A group of 20 people, both adults and children, go to watch a rugby match at Eden Park in Auckland New Zealand.
The group pay a total of $136 at the gate. The admission charges are: Adults $8 Children $4 
(a) If there are a adults in the group, how many children are there (in terms of a)?
(b) How much (in terms of a) do the adults pay?
(c) How much (in terms of a) do the children pay?
(d) Write an equation in terms of a.
(e) Solve this equation.
(f) How many children are there in the group?