Ответ:
г)5
Пошаговое объяснение:
\left \{ {{a^2-b^2=350} \atop {a=70-b}} \right.\\\\(70-b)^2-b^2=350\\\\4900-140b+b^2-b^2=350\\\\-140b=350-4900\\\\-140b=-4550\\\\140b=4550\\\\b=4550:140\\\\b=32.5\\\\" alt="\left \{ {{a^2-b^2=350} \atop {a+b=70}} \right.=>\left \{ {{a^2-b^2=350} \atop {a=70-b}} \right.\\\\(70-b)^2-b^2=350\\\\4900-140b+b^2-b^2=350\\\\-140b=350-4900\\\\-140b=-4550\\\\140b=4550\\\\b=4550:140\\\\b=32.5\\\\" align="absmiddle" class="latex-formula">

a²-b²=350
37.5²-32.5²=350
1406.25-1056.25=350
350=350
a+b=70
37.5+32.5=70
70=70
a-b=37.5-32.5=5