since the opposite of multiplication (5.7 times t) is division, you would divide 5.7 across the equal sign to 420. (420 divided by 5.7) so the answer would be t= 73.68... you can round that if it says too.
so, if a number or anything is right next to a variable (letter) like 5.7t for example, that is multiplication. same with if fractions are present, fractions would be division.
the opposite of multiplication is division, opposite of division is multiplication. and the opposite of addition is subtraction and the opposite of subtraction is addition.
whenever you cross over the equal sign, you use the opposite of what the original side did like add, subtract, multiply, or divide.