Answer:
x = 10
Step-by-step explanation:
The line from the vertex to the base is a perpendicular bisector.
Consider the left side right triangle, eith base = x
Using Pythagoras' identity.
The square on the hypotenuse is equal to the sum of the squares on the other 2 sides, that is
( x )² + 7² = ( )², that is
x² + 49 = 74 ( subtract 49 from both sides )
x² = 25 ( multiply both sides by 4 to clear the fraction )
x² = 100 ( take the square root of both sides )
x = = 10