Given equation :
.
Strategy 1: We can cross mutiply both sides remove fraction form.
On cross multiplication, we get
x * 7 = 3 * 42
7x = 126.
Dividing both sides by 7, we get
x = 18.
Strategy 2: We can find least common denominator(lcd) of both sides and multiplying both sides by that lcd to get rid denominators from both sides.
LCD of 42 and 7 is 42.
Therefore, multiplying both sides by 42, we get

x = 6 * 3
x = 18.