What is

(-18.278) - (-6.8)

(-18.278) - (-6.8) { first we have to open parenthesis or brackets of the equation }

-18.278 + 6.8 { - + - = + }

then we have to add both numbers and we get

-11.478 Ans

(-18.278) - (-6.8) = - 11.478 Ans

Do not add subtract a negative add

-18.278+6.8

it's a negative and positive so subtract the larger absolute value from the smaller absolute value and keep the sign.

-18.278+6.8