It isn't easy really but you can always divide the number out. For example 50% of 200 is 100 by dividing 200 by 2 or 25% of 100 is 25 by dividing 100 by 4 since 25% is equivalent to 1/4
X=7
You divide 14 by 2 to find the proportion (7) then multiply it by 1 to get the base length of the large triangle since they’re congruent.
The answer is -41
You can graph them and see where the line passes on the y-axis which is the vertical axis
