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:
Ann's age is seven-tenths of Bill's age.
a = .7b
:
In 4 years Ann's age will be eight-elevenths of bill's age.
(a + 4) = (b+4)
:
Multiply equation by 11:
11(a+4) = 8(b+4)
:
11a + 44 = 8b + 32
:
11a = 8b + 32 - 44
;
11a = 8b - 12
:
How old is Bill now.
:
Substitute .7b for a in the above equation
11(.7b) = 8b - 12
:
7.7b = 8b - 12
7.7b - 8b = -12
-.3b = - .12
b =
b = +40 yrs is Bill's age
:
:
To check solution find Ann's age .7(40) = 28 yrs
Check solution in the statement:
"In 4 years Ann's age will be eight-elevenths of bill's age."
(28+4) = (40+4)
32 = *44; confirms our solution
