You're nearly there. Just some more steps.
557 * x = 594 tells us
x = 594 / 557 (divide both sides by 557)
x ≈ 1.066427
When we've found this number we must realise the following:
the '1' in this answer is the 100% the car fixing costs (without taxes)
the '0.66427' stands for the tax rate.
To find the tax rate we multiply 0.66427 by 100, which gives us:
0.66427 * 100 = 6.6427 ≈ 7
So, rounded to the nearest %, the tax rate is 7%
This is an equation, you can't write equations as decimals. I think you're asking for x (as a decimal)?
Add 8 to each side: 4+8= 8+(-8)+3x
12=3x
x=4
This is a whole number so it's already in decimal form
Is that your test or homework
40000+1000x=60000
-40000. -40000
1000x=20000
x=20