45)
E = mc² <em> (solve for "m" by dividing both sides by c²)</em>
E/c² = m
46)
c(a + b) - d = f <em>(to solve for "a"; add "d", divide by "c" and then subtract "b")</em>
c(a + b) = f + d
(a + b) = (f + d)/c
a = (f + d)/c - b
47)
z = πq³h <em> (solve for "h" by dividing both sides by πq³)</em>
z/πq³ = h
48)
(x + y)/z - a = b <em> (solve for "y"; add "a", multiply by "z", and then subtract "x")</em>
(x + y)/z = b + a
(x + y) = z(b + a)
y = z(b + a) - x
53)
5x - 9 = 11x + 3
-9 = 6x + 3 <em>subtracted 5x from both sides</em>
-12 = 6x <em>subtracted 3 from both sides</em>
-2 = x <em>divided both sides by 6</em>
55)
5.4(3k - 12) + 3.2(2k + 6) = -136
16.2k - 64.8 + 6.4k + 19.2 = -136 <em>distributed 5.4 and 3.2</em>
22.6k - 45.6 = -136 <em>added like terms (16.2k + 6.4k and -64.8 + 19.2</em>
22.6k = -90.4 <em>added 45.6 to both sides</em>
k = -4 <em>divided both sides by 22.6</em>
57)
(4/9)y + 5 = (-7/9)y - 8
4y + 45 = -7y - 72 <em>multiplied by 9 to clear the denominator</em>
11y + 45 = -72 <em>added 7y to both sides</em>
11y = -99 <em>subtracted 45 from both sides</em>
y = -9 <em>divided both sides by 11</em>
