3 * x = 4y (from the question)
X+y = 21 (from the question)
3(21-y) = 4y (sub equation 2 in equation 1)
63-3y = 4y
Y=9 (now you sub the 9 instead of y in any of the equations and solve for x)
X=21-y = 21-9 = 12
Hope it helps, the logic is sound just go over the math.
Well...what are the expressions and phrases???
Number 1 and I think 4 not sure but try those .
40
substitute t = 10 into the expression
4t² = 4 × 10² = 4 × 100 = 400
now divide by 10 →
= 40
You basically just switch it around and subtract the fractions