To get the sum, put parenthesis around 1-4 and around 1-7 to indicate separate groups. Then, add the two groups.
Then, simplify by doing the operation inside each group.
`=-3 + (-6)`
Since the simplified form of the two groups have the same sign, to compute, add the numbers and copy the sign.
Hence, the sum of 1-4 and 1-7 is -9.