Do the following calculations and report the answers in scientific notation with the correct number of significant figures. Assume that all numbers were obtained from measurements.

a$.755+17\mathrm{.}66=$

b$.\frac{1\mathrm{.}1010-1\mathrm{.}1121}{1\mathrm{.}1121}=$

c$.(6\mathrm{.}0223{10}^{23})-(6\mathrm{.}0223{10}^{20})=$

d$.(4\mathrm{.}5{10}^4)-(4\mathrm{.}545)=$