0.4x + 3.9 = 5.78 Subtract 3.9 on both sides
0.4x + 3.9 - 3.9 = 5.78 - 3.9
0.4x = 1.88 Divide 0.4 on both sides
[tex]\frac{0.4x}{0.4}=\frac{1.88}{0.4}[/tex]
x = 4.7
[proof]
0.4x + 3.9 = 5.78 Plug in 4.7 for "x"
0.4(4.7) + 3.9 = 5.78
1.88 + 3.9 = 5.78
5.78 = 5.78
