we are given
Jim can lay bricks for a fireplace and chimney in 5 days
Jim's 1 day work is
we are given
With his father's help he can build it in 2 days
so, both can do same work in 2 days
so, both's 1 day work is
Let's assume
his father to build it alone in x days
his father 1 day work is
so, both's 1 days work is
so, we can set it to 1/2
we get
now, we can solve for x
now, we can cross multiply
now, we can solve for x
so,
his father to build it alone is
............Answer