Question 83423
0.5b+3.4=0.2b+12.4

= (0.5)b + 3.4 = (0.2)b + 12.4

multiplying throughout by 10 [as there is 1 place after the decimal point],

5b + 34 = 2b + 124

==> 5b - 2b + 34 = 124

==> 3b + 34 = 124

==> 3b = 124 - 34

==> 3b = 90

==> b = 90/3

==> b = 30