Respuesta :

Answer:

20.25

Step-by-step explanation:

21-3/4=20.25

Answer:

Step-by-step explanation:

a+b=21

a=21-b

b=3/4*a

b=3/4*(21-b)

b=3(21-b)/4

b=63-3b/4

4*b=63-3b

4b+3b=63

7b=63

b=63/7

b=9

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