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Step-by-step explanation:

From 6 to 9 is 3 units, the horizontal distance between C and D.  From 4 to 5 is 1 unit, the vertical distance between C and D.

Using the Pythagorean Theorem (or the closely related distance formula), we find the distance between C and D as follows:

distance between C and D:   sqrt(3^2 + 1^2) = sqrt(10)

c.

step-by-step explanation:

because first you have to add the 4x, 9x, and the 7x together and you get 20x and then you add the last numbers up and you get 5and then you put the subtraction sign in there and that's how you get the answer.