The uppercase T means "transpose". A matrix transpose is where you swap the rows and columns. Anything that is row becomes a column, and vice versa. What this means is that instead of a row vector, you end up with a column vector. The dimensions are important so you can properly multiply matrices.
Answer:
15
Step-by-step explanation:
Let's call Leah's age l and Rachel's age r. We can write:
l = 3r - 2 (1)
l + 3 = 2(r + 3) + 7 (2)
Substituting (1) into (2) we get:
(3r - 2) + 3 = 2(r + 3) + 7
3r + 1 = 2r + 13
r = 12
In 3 years Rachel will be 12 + 3 = 15 years old.
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