(0.00235M x (0.02L) x 40.08 g/mol Ca2+) / 0.1010g x100% =1.86%
I assume that all other data upto this point are correct, and your calculations can also be trusted. With this equation, however, there seems to be a problem. You are required to find out the w/w % of Ca in the main solution (from which the aliquot was taken).
But 0.00235 M x 0.02 L = moles of calcium in the aliquot, not the parent solution. Since the concentration of the aliquot and the parent solution are the same, you should use :
0.00235 M x 0.250L = mole of calcium in the 250 mL sample
I've not checked the numericals...