Question

А + B = 8, A*C = 21, B-D=5С*D= 9findА,В,С,D​

Answer 1

Answer:

A = 2.1

B = 5.9

C = 10

D = 0.9

Step-by-step explanation:

This is a long one

A + B = 8

my plan is to substitute B

B - D = 5

B = 5 + D

Now substitute D

C*D=9

D = 9/C

Now substitute C

A*C = 21

C = 21/A

Back to the D equation

D = 9/C

D = 9/(21/A) = 9A/21 = 3A/7

Back to B equation

B = 5 + D

B = 5 + 3A/7

Back to A equation

A + B = 8

A + (5 + 3A/7) = 8

7/7A + 3/7A + 5 = 10A/7 + 5 = 8

10A/7 = 3

10A = 21

A = 21/10 = 2.1

The rest should be simple

B = 5 + 3A/7

B = 5 + 3(2.1)/7 = 5.9

C = 21/A

C = 21/2.1 = 10

D = 9/C

D = 9/10 = 0.9