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See the answer below

Explanation:

From the graph, the concentration of salt solution where the number of burst red blood cells equals the number of intact ones is 0.40 g/100 cm3.

At this concentration, the percentage of burst cells is 50, meaning that the remaining 50% of the cells in the experiment remained intact.

The totality of the concentrations of all the salt solutions used is:

0.30+0.35+0.40+0.45+0.50 = 2 g/100 cm3

Thus, the percentage of salt solution concentration when the number of red blood cells that burst is the same as the number of red blood cells that do not burst equals;

          0.40/2 x 100% = 20%