Let X = the large #
Y = the small #
We have 2 unknowns, therefore we need 2 equations to solve for them:
X + Y = 61
X = 3Y - 7
Using the substitution method we get:
X + Y = 61 original equation
(3Y - 7) + Y = 61 substituting for X
4Y - 7 = 61 combine like terms
4Y - 7 + 7 = 61 + 7 add 7 to both sides
4Y = 68 simplify
4Y/4 = 68/4 divide both sides by 4
Y = 17 solve for Y
X + Y = 61 original equation
X + 17 = 61 replace Y with 17
X + 17 - 17 = 61 - 17 subtract 17 from both sides
X = 44 solve for X
Check your answer:
X + Y = 61 X = 3Y - 7
44 + 17 = 61 44 = 3(17) - 7
61 = 61 check! 44 = 51 - 7
44 = 44 check!
Therefore, the larger #(X) = 44 and the smaller #(Y)= 17.
