102
Why an approximate value when you know the exact value is 90! To the nearest thousand, for example, it is 0.
90
102. 12+90=102.
90+x+72+30 = 180. If you add 90+72+30, you get 192. But to get 180 you have to subtract 12. 90+(-12)+72+30 =180 if x is -12
702
The approximate value of 87 is 90 when rounded to the nearest ten. If you're looking for a more general approximation, it can also be considered as roughly 80, depending on the context.
7.8 + 12 = 19.8
90
10% of 90 = 990% 0f 10 = 9(10% of 90) + (90% of 10) = 18
If a + b + c + d + 80 + 90 = 100, then a + b + c + d = -70.
-90
The value of x that solves the equation -243 = 90 - 9x is x = -12.