Sam travel 20 miles in three hours. Sam walked part of the distance at a speed of 4 mph. Sam rode his bicycle for the remaining distance at a speed of 12 mph. How many hours did Sam spend walking? How many hours did Sam spend biking?

Sam sokey 0.5 hours biking and 3.5 hours walking

Step-by-step explanation:

Here, we want to know the number of hours spent walking and biking

Mathematically; distance = speed * time

Let the number of hours spent walking be x and the number of hours spent biking be y

Mathematically;

x + y = 3 •••(i)

distance spent walking = 4 * x = 4x miles

distance spent biking = 12 * y = 12y miles

4x + 12y = 20

divide through by 2

2x + 6y = 10 ••••••(ii)

From i , x = 4-y

Substitute this into ii

2(4-y) + 6y = 10

8 - 2y + 6y = 10

8 + 4y = 10

4y = 10-8

4y = 2

y = 2/4 = 0.5 hours

The number of hours spent walking = 4-0.5 = 3.5 hours