standard form for a linear equation means
• all coefficients must be integers, no fractions
• only the constant on the right-hand-side
• all variables on the left-hand-side, sorted
• "x" must not have a negative coefficient


2.1 is already in a decimal form.
Hope I helped!
I got 6.3 not sure if Im right
The answer is 180 i hope i helped you :)