ANSWER
4) 5x + 15 = 35
EXPLANATION
We're looking for an equation with the form:
[tex]y=ax+b[/tex]If we want this to have only one solution we have to give y a value. This value can be found since we're already given the solution x = 4:
[tex]y=5x+15[/tex]replacing x:
[tex]\begin{gathered} y=5\cdot4+15 \\ y=20+15 \\ y=35 \end{gathered}[/tex]Therefore the one-solution linear equation we can construct with this information is:
[tex]5x+15=35[/tex]