Answer:
Step-by-step explanation:
Step one:
given data
we are told that the expression for the depth of a lake after x years is given by
[tex]y=0.2x+42[/tex]
Required
The value of y when x= 4
Step two:
substitute the value of x in the expression to get y
[tex]y=0.2(4)+42\\\\y=0.8+42\\\\y=42.8\\\\[/tex]
After 4 years the depth will increase by 42.8 in