Bc is tangent to circle a at b and to circle d at c. what is ad to the nearest tenth?

Refer to the attached image. If we draw a line parallel to segment BC, and this line goes through point D, then we'll form the new point E. Point E is on segment AB.

The parallelogram EBCD parallelogram forms. In fact, this figure is actually a rectangle due to the right (90 degree) angles. By definition, the opposite sides are parallel. Consequently, the opposite sides are congruent.

So,
BC = ED = 24
EB = CD = 4

AE+EB = AB
AE+4 = 5
AE = 1

Note how triangle AED is a right triangle with the right angle at angle E.

We can use the pythagorean theorem to find x

a^2 + b^2 = c^2
1^2 + 24^2 = c^2
1 + 576 = c^2
577 = c^2
c^2 = 577
c = sqrt(577)
c = 24.0208

If we round to the nearest tenth, then we get 24.0 which is the final answer (so the answer is choice C)

Note: this is misleading as this implies that the hypotenuse is the same length as the leg, which is not the case. So this is one drawback to rounding. 

Num of plants = (original#ofplants)*(1.6)^t

The linear equation is: y=ax+b