Answer:
[tex]\red{ \bf \: c = {2}^{38} \: }[/tex]
Step-by-step explanation:
[tex] \bf c = ( {2}^{40}+{2}^{39}+{2}^{38}):7 [/tex]
[tex]\bf c = {2}^{38} \cdot( {2}^{40 - 38}+{2}^{39 - 38}+{2}^{38 - 38}):7 [/tex]
[tex]\bf c = {2}^{38} \cdot( {2}^{2}+{2}^{1}+{2}^{0}):7 [/tex]
[tex]\bf c = {2}^{38} \cdot( 4+2+1):7 [/tex]
[tex]\bf c = {2}^{38} \cdot7:7 [/tex]
[tex] \red{ \boxed{\bf \: c = {2}^{38} \: }}[/tex]
