Answer
Find out the how much did the baby gain in the last four months.
To prove
Let us assume that the baby gain in the last four months be x .
As given
A baby gains 11 pounds in its first year of life.
[tex]The\ baby\ gained\ 4\frac{1}{4}during\ first\ four\ months.[/tex]
i.e
[tex]The\ baby\ gained\ \frac{17}{4}\ during\ first\ four\ months.[/tex]
[tex]The\ baby\ gained\ 3\frac{1}{2}during\ second\ four\ months.[/tex]
i.e
[tex]The\ baby\ gained\ \frac{7}{2}\ during\ second\ four\ months.[/tex]
Than the equation becomes
[tex]x + \frac{17}{4} + \frac{7}{2} = 11[/tex]
[tex]x = 11 -\frac{17}{4} - \frac{7}{2}[/tex]
L.C.M (4,2) = 4
[tex]x = \frac{44 - 17 - 7\times2}{4}[/tex]
solving
[tex]x = \frac{44 - 17 - 14}{4}[/tex]
[tex]x = \frac{13}{4}[/tex]
or written as in the mixed fraction.
[tex]x = 3\frac{1}{4}\ pounds[/tex]
x = 3.25 pounds the baby gain in the last four months .