SOLUTION: Ann's age is seven-tenths of Bills age. In 4 years Ann's age will be eight-elevenths of Bills age. how old is Bill now?

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Question 129974: Ann's age is seven-tenths of Bills age. In 4 years Ann's age will be eight-elevenths of Bills age. how old is Bill now?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let a= Ann's age now
Let b= Bill's age now
a+=+%287%2F10%29%2Ab
In 4 years Ann will be a+%2B+4
In 4 years Bill will be b+%2B+4
a+%2B+4+=+%288%2F11%29%2A%28b+%2B+4%29
substitute a in the 1st equation for
a in the last equation
%287%2F10%29%2Ab+%2B+4+=+%288%2F11%29%2A%28b+%2B+4%29
%287%2F10%29%2Ab+%2B+4+=+%288%2F11%29%2Ab+%2B+%2832%2F11%29
multiply both sides by 11%2A10
7%2A11%2Ab+%2B+4%2A11%2A10+=+8%2A10%2Ab+%2B+10%2A32
77b+%2B+440+=+80b+%2B+320
3b+=+120
b+=+40
Bill is 40 now
check:
a+=+%287%2F10%29%2Ab
a+=+%287%2F10%29%2A40
a+=+28
a+%2B+4+=+%288%2F11%29%2A%28b+%2B+4%29
28+%2B+4+=+%288%2F11%29%2A%2840+%2B+4%29
32+=+%288%2F11%29%2A44
32+=+32
OK