2. Circle =50 square =0

3. 1+2+3+4+5+6+7+8*9= 100

1+2+3+4-5+6+...+20=200

4. 10 *(30+50)= 800 meters

800/(40-30)= 80 minutes

80 * (50+40) = 7200m

5. let a be xkm/h and b be 3/5 km/h.

(5+3)x=3/5*(5+3)+ 120

x=

6. let a xm/min and b ym/min.

1 120-4x=4y

56x- 1 120=56y

x=

y=

7.10 * (50-40) =100m

100/(40-30)= 10 minutes

10 * (50-30) = 200m

8.8*2= 16

8:08+ 16=8:32