Question 1103272
If using A, B, C, as variables for the measure of the corresponding interior angles, and A is the vertex point, B and C are the base angles, triangle isosceles, then:

{{{system(A=4y+10,B=75,C=3x)}}}


Angle mesures at B and C are equal (base angles of isosceles triangle).
{{{B=C}}}
{{{75=3x}}}
{{{highlight(x=25)}}}


What about A?
Both B and C each is 75 degrees.
{{{A+75+75=180}}}, sum of interior angles of any triangle;
{{{A=180-75-75}}}
{{{A=180-150}}}
{{{highlight_green(A=30)}}}
and you wer given an expression for measure of angle A.
{{{4y+10=30}}}
{{{4y=20}}}
{{{highlight(y=5)}}}