draw a diagram. you have a right-triangle with an acute angle being 20. cosine = adjacent/hypotenuse. so the side adjacent to the 20 degree angle is 24 and the hypotenuse is 25. You can find the remaining side using Pythagoras' theorem.

Now to find the sine and tangent. Recall that sine = opposite/hypotenuse and tangent = opposite/adjacent

we are in the fourth quad, so sine and tangent are negative

alternatively, you could use formulas. and