The formula for the area of a triangle is (b)(h)/2, where b=base lenth and h=height. In the first problem, b= 12 cm and h= 5 cm. Thus, the area is A = (12 cm)(5 cm)/2, or (60 cm^2)/2, or 30 cm^2 (answer).
Please, no more than 1 or 2 questions per post.