The river will not reach a level of 7 ft. after 5 hours.
A linear equation is in the form:
y = mx + b
where y, x are variables, m is the rate of change and b is the initial value of y.
Let y represent the height of the water level after x hours.
Since the river is 1 ft below its average water level and begins to rise by a constant rate of 1.5 ft per hour. Hence:
b = -1, m = 1.5. The equation becomes:
y = 1.5x - 1
To reach a level of 7 ft. That is y = 7:
7 = 1.5x - 1
1.5x = 8
x = 5.3 hours
The river will not reach a level of 7 ft. after 5 hours.
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