Let the person who digs the sand be X and the person who transports the sand be Y, because in order to transport the sand away.

So the tonnage of dredging and transporting sand should be the same, so

4*X=5*Y

Because 27=X+Y Y=27-X, so

4*X=5*(27-X)

4 X/5 = 27 X

4*X/5+X=27

9 X 5 = 27

X= 15

Because formula 4*X=5*Y

So 4* 15=5*Y

Y= 12

The answer is 15 people dig sand and 12 people transport sand.

2) If the speed of A is X, then the speed of B is x-2, because A is faster than B 10 meter for 5 seconds.

2(x-2)+4(x-2)=4x

The solution is x=6 x-2=4.

A: A is 6 and B is 4.