Fraction = part / whole. First find the part (money left), then express as a fraction of the whole. Always simplify.

Find the total amount spent.
Total spent	=	$14 + $10 = $24
Find the amount left.
Money left	=	$40 - $24 = $16
Fraction left = (money left) / (total money).
Fraction left	=	\(\dfrac{16}{40}\)
Simplify: GCD(16, 40) = 8.
Simplified	=	\(\dfrac{16 \div 8}{40 \div 8} = \dfrac{2}{5}\)