Answer:
16 litres = 100% of the tank capacity
x litres = 75% of the tank capacity (since 3/4 is equivalent to 75%)
To solve for x, we can cross-multiply and simplify:
16 * 75 = 100x
1200 = 100x
x = 12
Therefore, 3/4 of the tank capacity when the tank holds 16 litres is 12 litres.