The first dropdown box is "substitution" because we are replacing, aka substituting, the with . This replacement is valid because we are given that . They are congruent angles.
The second dropdown box is "definition of perpendicular". If we have a 90 degree angle like this, then the two lines are considered perpendicular simply by definition.
70-80=10 hope this help the 68 rounded to the nearest tenth equals 70 and 76 rounded to the nearest tenth equals 80 so if you subtract 80-70=10 Tito increased the percent up to 10 dollars