Answer:
measure of angle ABC is 6 degree.
Step-by-step explanation:
After you found x, you'll plug it in the equation of the angle it's asking for.
Measure of angle ABD, and you know measure of angle ABC = 4x-1.
4(1)-1 = 4-1 = 3
Measure of angle CBD = 2x+1.
2(1) +1 = 3
Measure of angle ABC is ABD + CBD
3 + 3 = 6
Second question:
sum of all the interior angle 180*(8-2)=1080 degree
sum of one interior angle 1080/8=135 degree
The area of deltoid is defined by formula:

Where e and f are diagonals.
If you were to double the size of either one. Let's say f. You would result with:

Which means if either of diagonals double in length the area of deltoid will be twice as big as it was before.
Hope this helps.
r3t40