What is the equation of 3x-2.5x = 1.9? Solve it in 90 minutes! I have limited time!

What is the equation of 3x-2.5x = 1.9? Solve it in 90 minutes! I have limited time!

3x-2.5x=1.9
0.5x=1.9
x=1.9÷0.5
x=3.8