You have three unknowns: examination hours, workshop hours and lecture hours. Then, we assign variables.
Let:
x - examination hours
y - workshop hours
z - lecture hours
Then, we formulate equations based on the relationships given.
x = 2y --> eq 1
y = 2z --> eq 2
Substituting eq 2 to eq 1,
x = 2(2z)
x = 4z
z = x/4
Therefore, the lecture hours cost one-fourth of the cost of the examination hours.
