You are riding your bike up Elm Trail towards Deer Trail. You plan to make a left turn on to Deer Trail. What is the angle measure of the turn?

90 degrees

Step-by-step explanation:

This question can be explained using the plan x and y axis.

Suppose you are moving from any positive point on x axis which can be considered Elm trail

let say point be (5,0).

Now you move at origin and

then take left turn,

your left turn at origin will be negative side of y axis(which can be considered Deer trail)

hence, you move on negative y axis.

Since we know that angle of intersection of x and y axis is 90 degrees.

Thus, angle measure of turn is 90 degrees.