A triangle's inside sides sum up to 180 degrees. So to find the angle y, just take 180 - the sum of the other two sides.
70 + 88 = 158
180 - 158 = 22
y = 22 degrees
Now, to find angle x, since x and y are next to each other on a straight line, it means they are supplementary angles. Supplementary angles add together to equal 180, so just substract y from 180 to get x.
