Let L=larger number; S=smaller number
L=2S+21 (larger number is twice the smaller number increased by 21)
S-L=-13 (smaller number minus the larger number because the difference is negative)
Substitute the L from the first equation into the second equation to get:
S-(2S+21)=-13
S-2S-21=-13 (distributive property)
Simplify to get S=-8
Then substitute S=-8 into the first equation to get L=5
So, the numbers are -8 and 5