Can someone explain step by step process

Answer:
Step-by-step explanation:
3*7*10*10*10*10*10*10*10
(5+2=7)(since is multiplication you add)
21*[tex]10^{7}[/tex]=B
2*10*10*10*10*10
4*10*10
(5-2=3)(since is division you subtract)
0.5*[tex]10^{3}[/tex]=c