Explanation

Let the number of sweets Roni gives to Tony be x.

After giving x sweets: Roni will have 2 25−x sweets.

Tony will have 55+x sweets.

We want Tony to have four times as many sweets as Roni, so: 55 + x = 4 ( 25 − x )

1. Expand the equation:

   $$55 + x = 100 - 4x$$
   

2. Add $4x$ to both sides to combine the $x$-terms:

   $$55 + 5x = 100$$
   

3. Subtract 5 from both sides:

   $$\mathrm{<font\; color="\#0000ff">5</font>}\mathrm{<font\; color="\#0000ff">x</font>}<font\; color="\#0000ff">=</font>\mathrm{<font\; color="\#0000ff">45</font>}$$5x = 45
   

4. Solve for $x$:

   $$$$x=45/5=9x