Answer
A constant value, say c, must be subtracted from the x-coordinates of all the points on the graph, to shift it by c units horizontally in the right direction. Thus, the variable x from the equation of the graph, say $f\left( x \right)$, must be replaced by $x-c$; that is, it must become $f\left( x-c \right)$.
Work Step by Step
When we replace x in each term of the function by $x+c$, the value of the function earlier obtained at x will now be obtained at the point $x-c$. This means the function is shifted by c units horizontally.
Let the function be $f\left( x \right)=2x$ and the graph be shifted horizontal right by $c$ units. Thus, all the x-coordinates of the points on the graph are decreased by c units.
Thus, the equation of the horizontally shifted graph in the right direction, by c units, is $f\left( x \right)=2\left( x-c \right)$
