Answer :

1.2x + 4.3 = 2.1 - x

add x

1.2x + 4.3 = 2.1 - x 
         +x           + x

Subtract 4.3

= 2.2x + 4.3 = 2.1
            -4.3         -4.3

= 2.2x = 2.1 - 4.3

divide by 2.2

2.2x = -2.2
 /2.2      /2.2

x = -2.2/2.2

x = -1.