subtracting a negative cancels them to become positve so now we have a + 1.8 = 5.4.
subtract 1.8 from both sides of a + 1.8 = 5.4 to isolate the variable and we have:
a = 3.6 because 5.4 - 1.8 is 3.6.
therefore a = 3.6. hope this helped! plug it into the original equation and you see that you get 5.4 = 5.4