Answer:
84
Explanation:
because the top and bottom lines are parallel, we can conclude that the 2 triangles (top and bottom) are similar triangles. This means the sides lengths of smaller triangle is proportional to the respective sides on the larger triangle. With this, we can form the following equation:
x/48 = 21/12 (multiply both sides by 48)
x = (21/12)· 48
x = 21 ·4
x = 84