David is making patterns using these rules. Rule for Pattern A: start with 20 and subtract 2 Rule for Pattern B: start with 10 and subtract 1 Which patterns did David make?

20,18,16,14,12,10,8,6,4,2

10,9,8,7,6,5,4,3,2,1

Step-by-step explanation:

Pattern A:

Rule : start with 20 and subtract 2

Pattern B:

Rule : Start with 10 and subtract 1

Pattern 1:

20 - 2 = 18

18 - 2 = 16

16 - 2 = 14

14 - 2 = 12

12 - 2 = 10

10 - 2 = 8

8 - 2 = 6

6 - 2 = 4

4 - 2 = 2

20,18,16,14,12,10,8,6,4,2

Pattern 2:

10 - 1 = 9

9 - 1 = 8

8 - 1 = 7

7 - 1 = 6

6 - 1 = 5

5 - 1 = 4

4 - 1 = 3

3 - 1 = 2

2 - 1 = 1

10,9,8,7,6,5,4,3,2,1

second option

step-by-step explanation:

the measures of a triangle equal 180. use that to find x.

2x+3x+4x=180

9x=180

9x/9=180/9

x=20

now you know x, you know angle a is 40°, angle b is 60°, angle c is 80°.

because angle a is 40°, the first option doesn't work.

because angle b is 60°, the second option does work.

when you add angle a and b, you get 100°. complementary means it equals 90°, so the third option doesn't work.

when you add angle a and c, you get 120°, which is not 100.