Answer :
Step-by-step explanation:
Let x be the number of households you mowed grass.
Let y be the number of households you shoveled snow.
From there, we know,
[tex]x + y = 22[/tex]
as equation 1.
next we also know,
[tex]150x + 225y = 3900[/tex]
as equation 2.
From here we know we can solve using simultaneous equations.
rearranging equation 1 with y the subject,
[tex]y = 22 - x[/tex]
Substitute this equation into equation 2.
[tex]150x + 225(22 - x) = 3900 \\ 150x + 4950 - 225x = 3900 \\ - 75x + 4950 = 3900 \\ - 75x = 3900 - 4950 \\ - 75x = - 1050 \\ x = - 1050 \div - 75 \\ = 14[/tex]
now substitute x = 14 into equation 1.
[tex]14 + y = 22 \\ y = 22 - 14 \\ = 8[/tex]
Therefore, you have mowed grass for 14 households and shovelled snow for 8 households.