估算下面各题。385+246≈50

估算下面各题。4_0a+]6C2@

385+246≈7d0X;t5}6l;m6D4_0a+]6C2@

508+198≈(M1e*i3W,J/n/Z/~4_0a+]6C2@

486+315≈+C6l6T,p2M)g1i3H8R.T-X8G:A6U'm/K4_0a+]6C2@

693-390≈(X8P4u/D(D-E8Q,F7X9i4_0a+]6C2@

463+35≈:[6E2x:s4M;\*v*S+[4_0a+]6C2@

280+321≈(`5a0q,@9b3f+x2K4_0a+]6C2@