By proportionality, for any number [tex]a[/tex], if T is multiplied by [tex]a[/tex] then the same goes for M.
a) M has been multiplied by [tex]\dfrac{3}4[/tex] hence [tex]T=20\cdot\dfrac{3}4=5\cdot3=15[/tex]
[tex]\boxed{T=15}[/tex]
b) T has been divided by [tex]2[/tex] hence [tex]M=\dfrac{4}2[/tex]
[tex]\boxed{M=2}[/tex]
