The smaller triangle is scaled by a factor of (18 cm)/(54 cm) = 1/3 of the larger triangle. The ratio of areas is the square of that scale factor.
small triangle area = (1/3)^2 × large triangle area
... = (1/9) × 603 cm^2
... = 67 cm^2
The appropriate choice is
... C. 67 cm^2
