By seeing this we know without looking at the triangles that EF is going to be the same as HJ because when they say a figure is the same as another and list the letters such as 'DEF' and 'GHJ' they will list them in the same order.
So
'DEF' = 'GHJ' we get:
'DE' = 'GH'
'EF' = 'HJ'
And we can do the last and first letters:
'FD' = 'JG'
And since we know 'EF' = 'HJ' and that they already told us 'EF' was 30, we know HJ will be 30.