“…In general, factors affecting students' quality and achievement in mathematics are internal and external factors (Purwanto, 2006;Dalyono, 2009;Slameto, 2010). Based on internal factors, several studies show that simultaneously interest and motivation affect mathematics achievement (Sukada et al, 2013), and motivation has a positive effect on learning interest (Surifah et al, 2016), and partially, interest is important to improve mathematics learning achievement (Lazarides & Ittel, 2012), interest related to academic achievement (Maurice, Dorfler, & Artelt, 2014), and student learning interest significantly influence learning achievement in mathematics (Schiefele & Csikszentmihalyi, 1995;Heinze, Reiss, & Franziska, 2005;Sembiring & Muktar, 2013;Kpolovie et al, 2014;Mutodi & Ngirande, 2014;Siagian, 2015;Tiara, Putri, & Isnani, 2015;Sirait, 2016), Motivation also significantly affects learning achievement in mathematics (Mbugua, 2012: Guvendir, 2016Basuki, 2015;Cleopatra, 2015;Sumantri & Whardani, 2017). encourage and increase student interest and motivation (Suparlan, 2005;Federici et al, 2016), teachers have an important role to influence students' interest in learning mathematics (Ivowi, 2001), and there is an influence of teacher's role as a motivator on student learning motivation (Sugiasih, 2015) Based on the above explanation, it shows that the teacher as a motivator is instrumental to influence the interest and motivation of students to excel in mathematics.…”