This
can be solve by simple addition and subtraction. Since the initial water in the
lake is 12 in below the normal starting by march, and it decreased further by 2
¼ in by the end of march and increased by 1 5/8 in by the end of april. So the
net water level is
L
= 12 – 2 ¼ + 1 5/8 = 12 5/8 in below the normal
