Question

If 21 − 3(a − 7) = a + 20, then find the value of a and check your results

Answer 1

21-3(a-7)=a+20
=> 21-3a+21=a+20
=> 42-3a=a+20
=> -4a=-22
=>2a=11
=>a=5.5

LHS
=21-3(5.5-7)
=21-16.5+21
=42-16.5
=25.5

RHS
5.5+20
=25.5

Therefore, LHS=RHS

Answer 2

21-3(a-7)=a+20
21-3a+21=a+20
42-3a=a+20
42-20=a+3a
22=4a
a=22/4
a=5.5

||CHECK||

21-3(5.5-7)=5.5+20
21-3(-1.5)=25.5
21+4.5=25.5
25.5=25.5