21(2-x)+12=44
multiply 21 by everything inside parentheses first
(21*2)+(21*-x)+12=44
42-21x+12=44
combine like terms
(42+12)-21x=44
54-21x=44
subtract 54 from both sides
-21x= -10
divide both sides by -21
negative divided by negative becomes positive
x= 0.476
Check:
substitute x=0.476 in equation
21(2-x)+12=44
21(2-0.476)+12= 44
21(1.524)+12= 44
32.004+12=44
44=44
Hope this helped! :)