Uilding a is 180 feet shorter than building b. the total height of the two buildings is 1490 feet. find the height of each building.

We will solve this using a system of equations.  We are first told that building a is 180 feet shorter than b, so our first equation is b = 180 + a.  Next we are told that the addition of a and b is 1490, so our second equation is a + b = 1490.  We already have the first equation solved for b, so let's sub that into the second equation in place of b: a + (180 + a) = 1490, and 2a + 180 = 1490.  2a = 1310, so building a is 655 feet tall.  b is 180 feet taller, so b = 655 + 180, and b = 835 feet tall.

What mathematical statement is missing ? ? the answer is b