check the picture below.
so the playground is really just 3 rectangles and one triangle, now the triangle has a base of 8 and a height of 6. We can simply get the area of each figure, sum them up and that's the area of the playground.

Multiply 8km/h by 4h. You will get 32 km
X=number total of student at the school.
70% of x=161
can suggest this equation:
(70/100)x=161
0.7x=161
x=161/0.7=230
Answer: the school has 230 students