Answer: it will take 12 years for both trees to be of the same height.
Explanation:
Let x represent the number of years that it will take for the blue spruce and the hemlock to be the same height.
A blue spruce grows an average of 6 inches per year. If a blue spruce is 4 feet tall,
1 inch = 0.0833 feet
6 inches = 6 × 0.0833 = 0.4998 feet
it means that its height in x years would be
0.4998x + 4
A hemlock grows an average of 4 inches per year. If a hemlock is 6 feet tall.
4 inches = 4 × 0.0833 = 0.3332 feet
it means that its height in x years would be
0.3332x + 6
The number of years that it will take both trees to be of same height is
0.4998x + 4 = 0.3332x + 6
0.4998x - 0.3332x = 6 - 4
0.1666x = 2
x = 2/0.1666
x = 12