The value of x, if ∆EFG ~ ∆TRS, is calculated as:
x = 6.
What are similar triangles?
Based on the AA similarity postulate, when two corresponding angles in two triangles are congruent, the two triangles are similar to each other, and this implies that their corresponding side lengths will be proportional in length to each other.
Since ∆EFG ~ ∆TRS by AA similarity postulate, therefore:
28/12 = 3x - 4/x
7/3 = 3x - 4/x
Cross multiply:
7x = 9x - 12
7x - 9x = -12
-2x = -12
x = 6