Question 828616
Length of side for square B, let this be w.
Length of side for square A is {{{(7/10)w}}}.


Area for square A is {{{(49/100)w^2}}}, and area for square B is {{{w^2}}}.


The question, "what percent of area of B is the area of A", means how much of area A is in area B?  You specified a percentage value for A in B.  

{{{((49/100)w^2)/(1*w^2)}}}
{{{49/100}}}
This is 49%.