Question 535279
Too many letters!
You need a common denominator that must be a multiple of all 3 denominators.
Because you do not know how t and c are related, we have to assume theyhave no factor in common. To have a multiple of c, we must include c as a factor in that number. To have a multiple of 3t, you need to include 3 and t as factors.
The product of 3, t, and c is a multiple of 3t, of t, and of c, and it's our least common denominator.
{{{4z/3t + 2y/t - x/c=(4z/3t)(c/c) + (2y/t)(3c/3c) - (x/c)(3t/3t)=4zc/3tc+6yc/3tc-3tx/3tc=(4zc+6yc-3tx)/3tc}}}