Atwo digit number is seven times the sum of its digits. the tens digit is 3 more than the units digit. what is the number

let x =  the tenth digit   and y the unit digit 

is seven times the sum of its digits.  7( x+y)  = 10 x +y 
7x + 7 y = 10x + y
3x =  6y     x= 6y / 3 = 2y    x= 2y 

we have that the tens digit is 3 more than the units digit so 
x = 3 + y
we replace it in the first equation   x= 2y
  3+ y = 2y 
 y=3 

and x= 6 
so the number is  63 

16) B: S = (n - 2)180

17) A: (n - 2)180/n

18) A: 60°

19) ∠e = 50°

20) D: 12°, 133°, 35°

21) D: 37°

Step-by-step explanation:

16) Generally, formula for finding sum of angles of a convex polygon with n-sides is; S = (n - 2)180

17) the measure of a regular polygon with n sides is; sum of interior angle/number of sides = (n - 2)180/n

18) sum of interior angles is 720.

In the diagram, there are 6 sides of the polygon.

Thus, each interior angle = 720/6 = 120°

Now, sum of angle on a straight line = 180°

Thus;

120 + ∠c = 180

∠c = 180 - 120

∠c = 60°

19) sum of interior angles is 910.

In the diagram, there are 7 sides of the polygon.

Thus, each interior angle = 910/7 = 130°

Now, sum of angles on a straight line = 180°

Thus;

130 + ∠e = 180

∠e = 180 - 130

∠e = 50°

20) sum of angles in a triangle is 180°

Thus, the set that will be correct is the one that has its sum equal to 180°. The only set that falls into this category is;

12°, 133°, 35°

22) Sum of interior angles in a quadrilateral is 360°.

Thus;

3x + 2x + 1 + x + 2 + 4x - 13 = 360

10x - 10 = 360

10x = 360 + 10

x = 370/10

x = 37