Question

I really need help
If AD = 12 and AC = 4y-36, find the value of y

Answer 1

notice the tickmarks

AD = DC

now AC, which is the whole length from side to side,
is 4y-36
AD is 12, and since DC is the same as AD, so
DC = 12

AC = AD + DC, or 12 + 12
now, we know AC is also 4y-36

so
`\bf \begin{array}{cccccclllllll} AC&=&AD&+&DC\\ \downarrow &=&\downarrow &&\downarrow \\ 4y-36&=&12&+&12\\ \\ \quad \\ \quad \\ 4y-36&=&&24 \end{array}`

solve for "y"