%A=\(\dfrac{A.100}{A+60}=28,57\)\(\Rightarrow\)100A=28,57A+1714,2
\(\Rightarrow\)71,43A=1714,2\(\Rightarrow\)A\(\approx24\left(Mg\right)\rightarrow MgCO_3\)
%B=\(\dfrac{B.100}{B+60}=40\)\(\Rightarrow\)100B=40B+2400
\(\Rightarrow\)60B=2400\(\Rightarrow\)B=40(Ca)\(\Rightarrow\)CaCO3