You can plug 1350 or less watts without overloading the circuit.
Step-by-step explanation:
Given, 
Circuit overloads at = 2400 watts 
Electricity consumed by portable heater = 1050 watts 
Let, 
x be the additional number of watts you can plug in.
Portable heater + additional watts ≤ Overloading limit 
1050 + x ≤ 2400
Subtracting 1050 from both sides 

You can plug 1350 or less watts without overloading the circuit.
Keywords: inequality, subtraction
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