INSTANCE adder#1;
extracted_from = {equation#1};
covers = equation#1;
addends = ?addends;
sum = expression#1;
END_INSTANCE;
INSTANCE adder#2;
extracted_from = {equation#2};
covers = equation#2;
addends = {expression#2, ?y};
sum = ?z;
END_INSTANCE;
INSTANCE adder#3; addends = ?addends; sum = ?sum; END_INSTANCE;