(x+54)-12=57
x + 54 – 12 = 57
x = 57 + 12 – 54
x = 15
26-(x-21)=42
26 – x + 21 = 42
– x = 42 – 21 – 26
-x = -5
x = 5
(x+54)-12=57
x + 54 – 12 = 57
x = 57 + 12 – 54
x = 15
26-(x-21)=42
26 – x + 21 = 42
– x = 42 – 21 – 26
-x = -5
x = 5