1 block: 19 houses = 20 blocks: Houses?

The equation x2 – 1x – 90 = 0 has solutions {a, b}. what is a + b?

Lance lived in portugal and brazil for a total of 14 months to learn portuguese. he learned an average of 130 new words per month when he lived in portugal, and an average of 150 new words per month when he lived in brazil. in total he learned 1920 new words. write a system of equations to represent the situation. use x to represent portugal, and y to represent brazil

Apositive number a or the same number a increased by 50% and then decreased by 50% of the result?