Answer:
a = 72 mm is the answer.
Step-by-step explanation:
a = ?
b = 21 mm
c = 75 mm
According to the Pythagoras theorem
a² + b² = c²
a² + 21² = 75²
a² + 441 = 5625
a² = 5625 - 441
a² = 5184
a = 72 mm
∴ a = 72 mm is the length of the missing leg.
