First, expand the terms in parenthesis by multiplying each term in the parenthesis by #color(red)(-3)#. Be careful to handle the signs of the individual terms correctly:
#(color(red)(-3) xx 2t) + (color(red)(-3) xx -4) + 2t = 4t - 3#
#-6t + 12 + 2t = 4t - 3#
We can now group and combine like terms on the left side of the equation:
#-6t + 2t + 12 = 4t - 3#
#(-6 + 2)t + 12 = 4t - 3#
#-4t + 12 = 4t - 3#
Next, add #color(red)(4t)# and #color(blue)(3)# to each side of the equation to isolate the #t# term:
#color(red)(4t) - 4t + 12 + color(blue)(3) = color(red)(4t) + 4t - 3 + color(blue)(3)#
#0 + 15 = 8t - 0#
#15 = 8t#
Now, divide each side of the equation by #color(red)(8)# to solve for #t# while keeping the equation balanced:
#15/color(red)(8) = (8t)/color(red)(8)#
#15/8 = (color(red)(cancel(color(black)(8)))t)/cancel(color(red)(8))#
#15/8 = t#
#t = 15/8#