What is the area of this shape?
units squared

19 units squared

Step-by-step explanation:

I have attached an image that explains the process.

Essentially we split the shape into 3 triangles, and solve the area of each, and add them up.

The top right triangle is 3 x 5. So A = (3 x 5) / 2 = 7.5

The bottom right triangle is a copy of the top right. So that A = 7.5

The triangle on the left is 4 long and 2 high. So A = (4 x 2) / 2 = 4 units.

Total area is:

7.5 + 7.5 + 4 = 19 units squared.

So we know that we only have 450 people coming to the event.

When the guests arrive, will everybody have a place to sit?
Chairs: 0.6 * 600 = 360, not enough since there are still 90 people standing.

Will there be enough meals?
Meals: 0.6 * 600 = 360, not enough since there are 90 people who doesn't have meals.

Enough dessert?
Deserts: 0.625 * 600 = 375 , not enough since 75 people left with no desserts.