How to calculate the equation 3x {x + 0.4} = 13.2

How to calculate the equation 3x {x + 0.4} = 13.2


3X{X+0.4}=13.2
3x+3 ×0.4 =13.2
3x +1.2-1.2 =13.2-1.2
3x=12
x=4



How to calculate 3x + 7 = 2.3x?


3x+7=2.3x
3x-2.3x=-7
0.7x=-7
x=-10