Given ray OC is perpendicular to ray OA and <DOA=135 degrees,what would be the measure of <DOC given that <COB=3x-7 and <BOA= -2x+4.

Huh? If the points A,B,C,D are in sequence, then since <AOC = 90,

<DOC = 135-90 = 45

If the angles are in some other order, then you may have to find x first.

I don't quite understand

To find the measure of ∠DOC, we need to make use of a few geometric properties.

First, we know that ray OC is perpendicular to ray OA. When two lines are perpendicular, the angle between them is 90 degrees. So, ∠COA = 90 degrees.

Next, we have ∠DOA = 135 degrees given. And since OC is perpendicular to OA, we can deduce that ∠DOA is split into two angles: ∠DOC and ∠COA.

Now, let's work with the angles ∠COB and ∠BOA.

Given:
∠COB = 3x - 7
∠BOA = -2x + 4

We know that the sum of the angles around point O is 360 degrees. So, we can set up an equation using the angles ∠COB, ∠BOA, ∠DOC, and ∠COA:

∠COB + ∠BOA + ∠DOC + ∠COA = 360

Substituting the given angles:
(3x - 7) + (-2x + 4) + ∠DOC + 90 = 360

Combining like terms:
x - 3 + ∠DOC + 90 = 360

Simplifying:
x + ∠DOC + 87 = 360

To isolate ∠DOC, we need to move the x term and the constant term to the other side of the equation:

∠DOC = 360 - x - 87

It appears that we are missing some information to determine x, which would then allow us to find the exact measure of ∠DOC. Please provide any additional information you may have.