Answer :
Given
[tex]f(x)=2.2x+1.9[/tex]For f(4) you have to calculate the value of the function when x=4.
To do so, replace the value in the formula and calculate
[tex]\begin{gathered} f(4)=2.2\cdot4+1.9 \\ f(4)=10.7 \end{gathered}[/tex]So for x=4, f(x)=10.7