The formula is 1/3*height*area of base.
Answer:

Step-by-step explanation:
1/2 ÷ -3/7 = -7/6 The answer is -7/6
The ad cost for half page Saturday after discount is
15% of 380 = 0.15×380 = 57
380 - 57 = 323
The ad cost for half page Tuesday after discount is
15% of 330 = 0.15×330 = 49.5
330 - 49.5 = 280.5
Cost of the ads for 10 Saturdays and 10 Tuesdays
(10×323)+(10×280.5) = 3230+2805 = 6035