Let the cost of a pen be dollars. Write an expression for the total cost of four pens and seven mechanical pencils in terms of .

4x +7 = ?  

Step-by-step explanation:

It was easy except you need more info to solve the equation

b. an equilateral triangle inscribed in a circle

step-by-step explanation:

we are given the figure of two circles having a triangle inside.

now, we know that,

"when a figure is lying inside an another figure, then the outside figure is known as circumscribed figure and the figure lying inside is referred to as the inscribed figure".

as we see that, the circles are containing the triangle completely.

thus, the circles are the circumscribed figures and the triangle is the inscribed figure.

hence, we get, 'an equilateral triangle is inscribed in a circle'.

in total they made   333.74 your welcome : d