This is normal IP routing. As long as you have default gateways on your computers pointing to the router this should work.
Can you post the output of:
/ip address print
/ip route print
/ip firewall filter print
/ip firewall nat print
[admin@admin] /ip address> print
Flags: X - disabled, I - invalid, D - dynamic
# ADDRESS NETWORK BROADCAST INTERFACE
0 11.1.1.1/24 11.1.1.0 11.1.1.255 Lan
1 10.1.1.4/24 10.1.1.0 10.1.1.255 Wan
2 111.1.1.1/24 111.1.1.0 111.1.1.255 Wifi
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[admin@admin] /ip route> print
Flags: X - disabled, A - active, D - dynamic,
C - connect, S - static, r - rip, b - bgp, o - ospf, m - mme,
B - blackhole, U - unreachable, P - prohibit
# DST-ADDRESS PREF-SRC G GATEWAY DISTANCE IN..
0 A S 0.0.0.0/0 r 10.1.1.1 1 Wan
1 ADC 10.1.1.0/24 10.1.1.4 0 Wan
2 ADC 11.1.1.0/24 11.1.1.1 0 Lan
3 ADC 111.1.1.0/24 111.1.1.1 0 Wifi
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[admin@admin] /ip firewall filter> print
Flags: X - disabled, I - invalid, D - dynamic
1 chain=input action=drop protocol=icmp src-address=11.1.1.0/24
icmp-options=8:0-255
2 ;;; allow established connections
chain=forward action=accept connection-state=established
3 ;;; allow related connections
chain=forward action=accept connection-state=related
4 chain=forward action=drop connection-state=invalid
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[admin@admin] /ip firewall nat> print
Flags: X - disabled, I - invalid, D - dynamic
0 chain=dstnat action=redirect to-ports=8080 protocol=tcp dst-port=80
1 chain=srcnat action=masquerade out-interface=Lan
2 chain=srcnat action=masquerade src-address=11.1.1.0/24
3 chain=srcnat action=masquerade out-interface=Wifi
4 chain=srcnat action=masquerade src-address=111.1.1.0/24
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