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Answer:
r = - 2.5

Step-by-step explanation:
21r - 7 - r + 5 = - 52
20r - 2 = - 52
20r - 2 + 2 = - 52 + 2
20r = - 50
20r ÷ 20 = - 50 ÷ 20
r = - 2.5
Since we know a triangle only has 180 degrees we can say:
99+3x+x+5=180
Then we can solve for x:
4x+104=180
4x=76
x=19
Answer:
N = 140
Step-by-step explanation:
N/7 = 20
Inverse operation of division: multiplication
N/7 = 20
becomes:
N = 7 x 20
N = 140
Thus, the value of N is 140.