The problem tells you that the two reactants react in a
This means that if you have the number of moles of KHP that took part in the reaction, you also have the number of moles of sodium hydroxide needed to get to the equivalence point.
Use the molar mass of KHP to determine how many moles you have in that sample
#0.7025 color(red)(cancel(color(black)("g"))) * "1 mole KHP"/(204.22 color(red)(cancel(color(black)("g")))) = "0.003440 moles KHP"#
This of course means that the reaction consumed
#c = "0.003440 moles"/(20.18 * 10^(-3)"L") = color(green)(|bar(ul(color(white)(a/a)"0.1705 mol L"^(-1)color(white)(a/a)|)))#
The answer is rounded to four sig figs.