If you rotate the triangle so that the 6 is on the bottom, the two sides are both 6.2.
Because the two sides are equal the two angles at the bottom would also be equal. One is given as 61 degrees, so the other bottom angle is also 61 degrees.
The three inside angles of a triangle need to equal 180, so X would equal 180 minus the two bottom angles.
X = 180 - 61 - 61 = 58 degrees.