Step-by-step explanation: We can see that the triangles are similar by the AA Triangle Similarity Theorem (90 degree angle and vertical angle), so we can use the scale factor to find x. The scale factor is 1:2 because the side on the smaller triangle is 2 units and the corresponding side on the larger triangle is 4 and 2:4 = 1:2. Next we have to structure the equation. Using the scale factor, we multiply 3.5 by 2 to get the length of the corresponding side in the larger triangle. Now we know that x = 3.5*2. 3.5*2 = 7, so x = 7.
