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The sum of three numbers is 72
The second number is 7 times the first.
The third number is 18 less than the second.
What is the first number?

Sagot :

Leora03idn

Answer:

6

Step-by-step explanation:

Let the first, second and third numbers be a, b and c respectively.

a +b +c= 72 -----(1)

b= 7a -----(2)

c= b -18 -----(3)

Substitute (2) into (3):

c= 7a -18 -----(4)

Substitute (2) and (4) into (1):

a +7a +7a -18= 72

Simplify:

15a -18= 72

Add 18 to both sides of the equation:

15a= 72 +18

15a= 90

Divide both sides by 15:

a= 90 ÷15

a= 6

Thus, the first number is 6.

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