Find x

If GF is parallel to AB....we have a theorem that says that a segment in a triangle drawn parallel to a base divides the sides proportionally

Specifically :

48 / 84  =  52 / [ 7x + 7]

4/7  =  52/ [7x + 7]     cross-multiply

52 * 7  =  4 [ 7x + 7 ]    simplify

364  =  4[ 7x + 7]       divide both sides by 4

91  =  7x + 7     subtract 7 from both sides

84  =  7x      divide both sides by 7

12  = x

Your third one is correct....!!!

Second one

MLN  = BAC   ....so....

ML/LN  = BA/AC

35 / 45  =  [ -13 + 2x ] / 9

7/9  = [ -13 + 2x] / 9     multiply both sides by 9

7  =  -13 + 2x       add 13 to both sides

20  = 2x    divide both sides by 20

10  = x