Subtract from Sides

What: Subtract the same expression from the both sides of ==
Why: Such side-wise subtraction is an essential computation for solving equations
Time To Complete: 3 hours 

eq = (x -3 == 17*y + 9);

lhs = eq.left - 9; 
rhs = eq.right - 9;

eq2 = (lhs == rhs);

show eq2;

save as sides;

Output

"eq2" → -12 + x == 17*y