You need to isolate the variable g onto one side. Since we're going backwards, we need to do the opposite of the order of operations. Step one is to subtract 20g from both sides. 17g-20g is -3g. -3g+6=3. Now, subtract 6. 3-6=-3.
-3g=-3. Finally, divide both sides by -3. -3/-3 is 1, so G is 1.
