If 21 is added to (+ 21) a number (x) the result (=) is 40 less than (- 40) twice the number (2x)
x + 21 = 2x - 40 Add 40 to both sides
x + 61 = 2x Subtract x from both sides
61 = x Switch the sides to make it easier to read
x = 61
X+y=27
x=2y
2y+y=27
y=9
x=27-y
x=27-9=18
300 + 0+ 1, 200 + 50+ 6, 800 +70 + 8.
