C t//v u//w this can be solved by analyzing the angles angles on t and v are supplementary which makes them same side exterior angles angles on u and w are supplementary making them same side interior angles
mathematically the answer to that is 18 because 10.2 minus 2.4 is equal to the difference of 7.8 and 7.8 plus 10.2 is equal to the sum of exactly and positively 18